Boxing, wrestling, and MMA - all have tough individuals, but who is the toughest of them all? Who would be left standing if an open tournament would take place tonight?

Determining who is the best in combat sports often goes hand-in-hand with determining who is the biggest and best. The reason combat sports have weight classes is that it is assumed that a bigger man should beat a smaller man. Any follower of combat sports knows this does not always happens, but when ranking the best of the best, preference should be given to the bigger competitors. While a skilled small fighter can beat a bigger fighter, he should not expect to beat a bigger fighter just as skilled as he is. Thus, the fighters on this top 20 list all compete at over 155 pounds or 70 kilograms. Also, fighters who have a recent validated failed drug test or are unfit to fight because of injuries are excluded.

When determining the rankings, preference is given to fighters (especially those who are strikers) who have a clear ability to finish a fight, and just do not expertly operate the scoring system in their particular sport. For boxers, this means they should have a great knockout percentage. So, without further adieu, here are the 20 best fighters on the planet.

20 20. Nieky Holzken - Kickboxer, 89-11, 46 Knockouts

The best welterweight (170 pounds) kickboxer in the world, Nieky Holzken has not lost since 2012. The Glory title holder first put himself in position to get Glory’s welterweight belt after stopping Joseph Valtellini in the finals of the promotion’s welterweight tournament in December of 2013. Then, after an injury-plagued 2014, Holzken finally won the welterweight title in 2015 after two consecutive stoppages of Raymond Daniels. Since then, Holzken has had two successful title defenses.

Holzken is often praised for the quality and the relentlessness of his striking, as over half of his wins have come via knockout. That knockout ratio is very impressive for a kickboxer with as many fights as Holzken. He also has an 11-0 record with eight knockouts as a professional boxer. That gives another indication of his striking, although his competition as a boxer has not been the best.

19 19. Sergey Kovalev - Boxer, 30-0-1, 26 Knockouts

Nicknamed “Krusher,” the 33-year-old Russian light heavyweight has run roughshod over his competition since starting his pro career in 2009. He’s bashed former champions Nathan Cleverly and Jean Pascal (twice), while out-boxing another former champion in sage pugilist Bernard Hopkins. Sergey Kovalev has not come close to losing a fight since his split decision win over Darnell Boone in 2010. Even the blemish on his record, a draw with Grover Young, was the result of Young being struck by an accidental blow in the back of the head.

Kovalev’s prowess in the ring has made it tough for him to find opponents. Most notably, Kovalev has called-out fellow hard-punching light heavyweight Adonis Stevenson for not agreeing to fight him. Kovalev looks to finally get another test in the fall when expert boxer Andre Ward is expected to step up and face him this fall.

18 18. Artur Beterbiev - Boxer, 10-0, 10 Knockouts

Artur Beterbiev is another light heavyweight boxer from Russia, and while he does not hold the accolades as a professional that Kovalev holds, Beterbiev was the better boxer when the two were coming up in the amateur ranks in Russia. He beat Kovalev and eliminated him from contention from the 2007 Russian World Championship team. Unlike Kovalev, Beterbiev remained an amateur until after the 2012 Olympics, and did not have his first professional fight until 2013.

However, in just three years, Beterbiev has fought his way into virtually every top-10 ranking of light heavyweights. No fighter has lasted more than seven rounds with Beterbiev. That is where an overmatched Alexander Johnson was dropped three times. Beterbiev’s most notable win came over the apparently “shot” fighter Tavoris Cloud. Beterbiev finished Cloud in the second round, faster than both Adonis Stevenson and Bernard Hopkins could do before him in Cloud’s only two previous defeats.

17 17. Oleksandr Usyk - Boxer, 9-0, 9 Knockouts

If you continue to follow the degrees of separation from Sergey Kovalev and Artur Beterbiev, you will get to the 29-year old Ukrainian Cruiserweight Oleksandr Usyk. Usyk won gold medals at the 2011 World Championships and 2012 Olympics, beating Beterbiev on his path to gold both times. Usyk also turned pro in 2013, like Beterbiev, and has foray into the professional ranks has gone just as smooth. No Usyk fight has gone the distance, with South African Danie Venter lasting the longest as he finally was put away in the ninth round.

Whatever Usyk has done up to this point will be put in its proper perspective this September when he challenges the undefeated Krzystzof Glowacki for his WBO Cruiserweight title in his native Poland. If Usyk wins this fight, he will become a world champion in just his 10th professional outing, and will have plenty of prime years left.

16 16. Marcus “Buchecha” Almeida - BJJ, 4 x Absolute World Champion

The first non-striker on the list comes from a discipline that had success against strikers in the early days of MMA. Brazilian jiu-jitsu practitioners do not enjoy the advantages they did when the martial art was just making its way into the mainstream, but Fabricio Werdum recently showed how viable BJJ still is by holding the UFC Heavyweight title for about a year.

The biggest and best BJJ practitioner going right now is Buchecha, Marcus Almeida. Weighing around 220 pounds, Almeida has the ground game of someone much smaller as evident by how extremely hard it is to submit him. He has dominated major tournaments over the last three years, and it seems that a jump to MMA is in his future. That is when we will see can Almeida take strikes. If he can, his BJJ should make him tough to beat.

15 15. Simon Marcus - Kickboxer, 44-2, 24 Knockouts

Simon Marcus, Glory’s middleweight (187 pounds) champion, began his professional kickboxing career with a bang as he went nearly six years before losing. During that stretch, Marcus dethroned Artem Levin for the title of best 175-pounder in the world. Marcus’ only two defeats came within a six-month span that started in June of 2014, with the first of those losses being his debut under the Glory banner. That defeat came at the hands of Joe Schilling, who he had already defeated twice.

Marcus rebounded from that setback, and once again prevailed over Levin. This time, it was for the Glory middleweight belt however, and Levin basically refused to continue to fight after a scoring dispute. Nevertheless, Marcus is a powerful striker who is also one of the most respected Muay Thai practitioners on the planet. With those traits, he can stand with almost anyone.

14 14. Anthony Joshua - Boxer, 17-0, 17 Knockouts

With his second-round knockout of an overmatched Charles Martin back in April, Anthony Joshua became the fifth fastest boxer to win a world heavyweight title. The 6-foo-6 26-year old IBF Heavyweight Champion from England has already defended his belt, knocking out the even taller Dominic Breazeale (6-foot-7) in June. Joshua first became known because of his amateur career, winning gold at the London 2012 Olympics, thus solidifying him as a national hero and a name to remember.

Many in the boxing community think Joshua needs to hone his craft more in order to compete with a couple of the bigger names in the heavyweight division. Those big names just happen to be as big as he is, but because of his ability to end fights with his punching power, there are not too many people in the world he should not be able to whoop in a no-holds barred fight.

13 13. Michael “Venom” Page - MMA, 11-0, 7 Knockouts, 3 Submissions

You might have to go as far as back to the legendary Bruce Lee to find opinions of a martial artist ranging from ‘he’s the best in the world’ to ‘he can’t beat the neighborhood bully.’ The mixed reviews on Michael Page are in part because of his flashy style, which makes it seem like he is preoccupied more with dancing to imaginary music in his head than knocking someone out. However, he often ends up knocking someone out.

Page should not be taken as a gimmick as he won 10 light or semi contact world kickboxing championships from the age of 12 to 22. After turning to MMA, Page has shown the ability to end matches with submissions and defend submission attempts while he is on the ground. He still must prove himself against better competition, but Page’s skills make him one of the most dangerous strikers in the world.

12 12. Stephen “Wonderboy” Thompson - MMA, 13-1, 7 Knockouts, 1 Submission

Coming from the same hands down fighting background that Michael Page hails from, Stephen “Wonderboy” Thompson is the most accomplished of the flashy, former kickboxers who have made their way into MMA. There is no concern over Thompson’s level of competition, as Thompson is the UFC’s No. 1 contender at welterweight. A match with the winner of the Robbie Lawler (champion) vs. Tyron Woodley title match is in the offing for Thompson, and he has the skills to give either fighter trouble.

Thompson’s last three wins are over big names Rory MacDonald, Johny Hendricks, and Jake Ellenberger – with the wins over Hendricks and Ellenberger coming on highlight-reel stoppages. His success in MMA comes on the heels of his professional kickboxing career, where he went 20-0. He also won 37 out of 38 kickboxing matches as an amateur with one no contest.

11 11. Khabib Nurmagomedov - MMA, 23-0, 8 Knockouts, 7 Submissions

Competing at a weight smaller than anyone one the list, Khabib Nurmagomedov has a multifaceted fighting background. He is a two-time World Combat Sambo Champion, a BJJ world champion, and has a black belt in Judo. Having already used the disciplines that would make him successful in MMA, Nurmagomedov took to the sport like a fish to water. When he is not ending fights, he owns them, often tossing his opponents around like a ragdoll. Of his 23 wins, seven are in the UFC, and he was the last man to beat former lightweight champion Rafael dos Anjos – before Eddie Alvarez did so earlier this month.

Only injuries that sidelined him for two years have kept Nurmagomedov from fighting for a UFC title of his own. Even if his everyday weight is much higher than his weigh-in weight, Nurmagomedov has the skills at 155 pounds to beat quality, bigger fighters.

10 10. Jordan Burroughs - Freestyle Wrestler, 3 x World Champion, 1 Olympic GoldMedal

Perhaps the most dominant freestyle wrestler on the planet, Jordan Burroughs is on the short list of those often mentioned as that sport’s pound-for-pound king. Burroughs holds a record of 124-2 in U.S. and international competition, as he has been virtually unbeatable since winning back-to-back NCAA National Championships to conclude his career at Nebraska. After exhausting his eligibility at Nebraska in 2011, Burroughs started his professional career with 69 straight wins – meaning he had won 140 consecutive matches when his last two collegiate seasons were factored in.

The second of his career losses was in large part due to him having to fight through a knee injury. Still, in those 2014 World Championships where the loss and injury occurred, Burroughs was good enough and tough enough to win a Bronze medal despite the hurt knee. With the success wrestlers have in MMA competitions, you would have to like Burroughs chances against fighters from other disciplines.

9 9. Bilyal Makhov - Freestyle/Greco-Roman Wrestler, 3 x World Champion

While it is speculation on how most of the wrestlers on this list would fare against fighters from other disciplines, how Bilyal Makhov would fare will soon be known. Makhov signed a contract to fight in the UFC last year, but is waiting to potentially compete in the 2016 Olympics before fighting. Nevertheless, he has trained in MMA, and those in his camp think he is a future UFC Heavyweight Champion.

Makhov won gold medals in the 2007, 2009, and 2010 Freestyle World Championships, and bronze medals in the 2014 and 2015 Greco Roman World Championships, making him the first person in nearly half a century to medal in both championships. Only 28 years old, the 6-foot-5, 260-plus pounder is in position to add to his wrestling superlatives and become one of MMA’s best fighters, making him one of the world’s best.

8 8. Cain Velasquez - MMA, 14-2, 12 Knockouts, 1 Submission

As it is the case with great fighters, a loss should not change one’s opinion of Cain Velasquez. Velasquez lost his UFC Heavyweight Title a year ago to Fabricio Werdum. Velasquez returned to the octagon in July and pounded out a first-round stoppage of Travis Browne. The loss to Werdum and a knockout at the hands of Junior dos Santos are the only losses Velasquez has suffered in his MMA career, so to beat him in a fight one likely would have to end the fight early.

Velasquez is a former NCAA All-American wrestler and is known for his intensity and cardio. He has earned a black belt and BJJ and also practices Muay Thai. Injuries have kept him from competing as much as he would like in recent years, so barring an injury before “tonight’s” tournament, he makes the list.

7 7. Wladimir Klitschko - Boxer, 64-4, 53 Knockouts

Wladimir Klitschko achieved a level of dominance not often seen in the highest level of combat sports. From 2005 to 2015, the heavyweight boxer was so dominant that his fights became to be viewed as boring. This was mainly because his opponents had little chance of winning. Often categorized as a low-risk taker, the fact that Klitschko often finished fights early should not be overlooked. His knockout percentage of 82 percent is one of the highest ever for a heavyweight.

He, along with his brother Vital, signified a change in boxing’s heavyweight division, one that carved out sort of a super heavyweight division out of the bigger heavyweight fighters. Riding on the back of Lennox Lewis, who dominated the division just before the Klitschko’s did, the 6-foot-6, 246-plus pound Wladimir has proven to be a tough match for anyone in a standup fight.

6 6. Khadzhimurat Gatsalov - Freestyle Wrestler, 5 x World Champion, 1 Olympic Gold Medal

Speaking of dominance, perhaps no wrestler was as dominant as Khadzhimurat Gatsalov was from 2004 to 2013. After winning gold at 96 kilograms (211.6 pounds) in the 2004 Olympics, Gatsalov went on to win four world championships at that weight, and another at 120 kilograms (264.5 kilograms) in 2013. Notably, Gatsalov shut out current UFC light heavyweight champion Daniel Cormier in the 2004 Olympic semifinals, ruining Cormier’s chances of a guaranteed medal. In fact, Gatsalov is thought of so highly by Cormier that he trained with Cormier, leading up to the MMA fighter’s January 2015 fight with Jon Jones.

At 33, Gatsalov is three-and-a half years younger than Cormier, so he is far from being washed up – despite his last world championship coming in 2013. He is another wrestler who eventually may look to prove himself in MMA.

5 5. Anzor Boltukaev - Freestyle Wrestler, Reigning European and Russian Champion

The hottest wrestler at 97 kilograms going right now is Anzor Boltukaev. Over the last year, he has won three major events, defeating world champion Kurt Snyder, Olympic champion Jakob Varner, and fellow Russian countryman Khadzhimurat Gatsalov in the process. In the finals of the 2016 Russian National Championships, Boltukaev dispatched Gatsalov 10-0 in 62 seconds via technical fall. Boltukaev also dominated the 2016 European Championships, only being tested by 2012 Olympic silver medalist and 2014 World Championship bronze medalist Valeriy Andriytsev of Ukraine. No other wrestler scored against Boltukaev at the European Championships.

Although he is already 30-years old, Boltukayev seems to be just coming into his prime, though he was no slouch before his recent run. Boltukaev won bronze at the 2013 World Championships, losing only to eventual silver medalist and 2010 World Champion Khetag Gazyumov of Azerbaijan.

4 4. Daniel Cormier - MMA, 18-1, 7 Knockouts, 4 Submissions

After going undefeated in his short time as a heavyweight, and then dropping down to light heavyweight and defeating all comers with the exception of Jon Jones, it is not a leap to view Cormier as the top fighter in the UFC. The former freestyle wrestler has adapted greatly to MMA, as before coming to the UFC he ran through Antonio Silva and Josh Barnett to become Strikeforce’s last heavyweight champion. His lone career loss to Jones may become to be seen in a better light, depending on how Jones’ career goes after his recent failed drug test.

Cormier’s domination of some of the biggest men in MMA with his wrestling gives him a chance to be competitive against anyone fighting in combat sports. That, with his improved striking and BJJ since coming to MMA, gives him a chance to defeat anyone.

3 3. Abdulrashid Sadulaev - Freestyle Wrestler, 2 x World Champion

Abdulrashid Sadulaev has dominated the last two-plus years. The 20-year old Russian has vaulted himself into being looked at as the best pound-for-pound freestyle wrestler in the world by many. He has won gold in every competition he has placed in since 2014, including both the 2014 and 2015 World Championships. Sadulaev was barely challenged in his world championship victories, and that fact adds to the perception of his invincibility.

Wrestling predominantly at 86 kilograms (189.5 pounds) during that time span, Sadulaev has also competed at 97 kilograms. He won gold at the 2015 European Nations Cup at that weight. On a Russian team that is loaded with talent, as this list indicates, the young gun Sadulaev stands head and shoulders above his teammates. Being arguably the world’s best wrestler makes it very difficult for anyone to beat him in a fight.

2 2. Vitaly Minakov - MMA, 18-0, 9 Knockouts, 7 Submissions

Another Russian combat sport participant, who is virtually unbeatable right now, Vitaly Minakov has run off an undefeated MMA record across several promotions. The former Bellator heavyweight champ started in M-1 Global and most recently fought EFN. Without the high profile of some of his UFC counterparts, Minakov’s pedigree still makes a case for him as one of the toughest fighters on the planet. Virtually a legend in sambo, Minakov joins Fedor Emelianenko as being two of only three men to win four Combat Sambo World Championships. Minakov’s four Russian championships in the discipline only trails Emelianenko’s six.

Also, similarly to Emelianenko, Minakov previously excelled in one of the disciplines that inspired sambo, judo. Just 31 years old, Minakov may be building his own Fedor-type career of being the most unbeatable MMA fighter in the world. His skill set suggests he may be.

1 1. Teddy Riner - Judo, 8 x World Champion, Olympic Gold Medalist

Imagine Ronda Rousey with the height of LeBron James, the weight of J.J. Watt, and the cat-like quickness and nimbleness of a professional break dancer. That is what you get in the package of Teddy Riner – all 6-foot-8, 290 pounds of him. The Frenchmen has not lost a judo match since 2010. His eight world championships include his first world title, when he was the tender age of 17 – making him the youngest judoka ever to win a world title. He is the most dominant combat sports athlete in the world right now.

Having size, athleticism, and the technique he has shown in judo, Riner could make quick work of a lot of combat sport athletes worldwide. Rousey showed how valuable aspects of judo, like throws, can be in MMA. Riner in a fight against most athletes might be simply put, unfair.