John Cena became the face that runs the place in the Ruthless Aggression Era. Cena improved drastically from his debut in 2002, and a couple of years later he won the United States Championship. In 2005, Cena finally won the WWE Championship, and he was drafted from SmackDown to Raw, and that's where he cemented his position as the undisputed face of the company.

RELATED: 5 John Cena Matches Dave Meltzer Overrated (& 5 He Underrated)

Cena was involved in several top-level feuds against some of the all-time greats in the business. Some of the talents that clashed with Big Match John elevated him to the next level. Whilst, Cena was at the top of his game in the Ruthless Aggression Era, some of the feuds that he was involved in were underwhelming, but the majority were fantastic.

15 The Great Khali

One of the worst feuds in John Cena's career was feuding with The Great Khali in 2007. Khali's in-ring movement was languid, and Cena retained the WWE Championship against Khali at Judgment Day.

That wasn't the end of their feud because Khali's foot was dangling outside of the ring ropes when Cena cinched in the STF. Their rivalry culminated at One Night Stand with Cena retaining the WWE Championship in a Last Man Standing match.

14 Rene Dupree

One of John Cena's first major rivals over the United States Championship was Rene Dupree. Dupree was drafted from Raw to SmackDown, and Cena successfully defended the United States Championship at Judgment Day 2004.

They clashed once again on the May 20, 2004, edition of SmackDown, but Dupree won via count-out. They battled the following week on SmackDown with Cena retaining the US Title in a Lumberjack match. Their matches weren't the greatest, but Cena won the feud.

13 Big Show

John Cena was chasing his first piece of silverware when he challenged Big Show for the United States Championship at WrestleMania 20. This was the curtain-raiser at WrestleMania, and the World's Largest Athlete was carrying an injury in this bout.

RELATED: Every US Title Match In WrestleMania History, Ranked Worst To Best

They had a decent match, and Cena had to work hard to get the job done. Show kicked out of the FU, but Cena used his chain and a second FU was enough for Cena to win the United States Championship at his first WrestleMania.

12 Booker T

Booker T had a wealth of experience inside the squared circle, and he squared off with John Cena in a best-of-five series over the United States Championship. Cena won the first fall at SummerSlam 2004, but Booker T won the next two falls in succession, and he was one away from keeping the United States Championship.

Cena evened the scores at 2-2, and the winner of their meeting at No Mercy 2004 would be the United States Champion. They had a decent battle, and Cena recaptured the US Championship from Booker.

11 The Undertaker

John Cena was a heel for half of 2003, and he had a mouthwatering feud with The Undertaker. Cena's in-ring skills improved when he feuded with the American Badass.

Their match at Vengeance 2003 was underrated, and Undertaker picked up the win over Cena. Moreover, Cena earned a huge win over Undertaker on SmackDown with some help from A-Train, and Cena ended up winning his feud with The Undertaker.

10 Brock Lesnar

The rivalry between John Cena and Brock Lesnar is fondly remembered from Lesnar's return to WWE in 2012, but they briefly had a feud in 2003. Cena became the number one contender for Lesnar's WWE Championship at Backlash 2003.

RELATED: 10 Best Finishers Of WWE's Ruthless Aggression Era

Lesnar was the more experienced of the two in the main event scene, and he had two WWE Championship reigns to his name. Nevertheless, Cena gave it his best shot, but he failed to beat Brock for the gold at Backlash.

9 Rob Van Dam

Rob Van Dam won the Money in the Bank ladder match at WrestleMania 22, and a month later he announced that he'd cash in his Money in the Bank briefcase against John Cena for the WWE Championship at ECW One Night Stand 2006.

Their rivalry was short-lived, but their WWE Championship match was outstanding. The atmosphere was electric, and RVD defeated Cena for his first WWE Championship and the atmosphere was electric with Cena on the receiving end of a hostile reception.

8 JBL

John Cena and JBL's rivalry over the WWE Championship at WrestleMania 21 saw the changing of the guard. Cena defeated JBL for his first WWE Championship reign, and he defeated him in a rematch in an "I Quit" match at Judgment Day 2005.

They rekindled their rivalry in 2008 when both men were members of Raw. Their battles were always competitive with Cena prevailing at Judgment Day and One Night Stand, but he lost their New York City Parking Lot Brawl at The Great American Bash.

7 Umaga

Towards the end of 2006, John Cena was engaged in a feud with Umaga and Cena's WWE Championship reign was in huge jeopardy as the Samoan Bulldozer was unbeaten.

RELATED: 10 Things WWE Fans Need To Know About Their New Year's Revolution PPV Shows

Cena ended Umaga's unbeaten streak at New Year's Revolution 2007, and their rivalry culminated in a Last Man Standing match at the 2007 Royal Rumble. They hit a home run in a breathtaking WWE Championship match with Cena getting the job done once again to remain as WWE Champion.

6 Chris Jericho

John Cena was the reigning WWE Champion when he was drafted from SmackDown to Raw, and Chris Jericho was his first major rival on the red brand in 2005. Cena and Jericho had good chemistry together, and before their WWE Championship match at SummerSlam, they had a battle of the bands.

Cena defeated Jericho to retain the WWE Championship in a hard-fought battle, and 24 hours later, Cena beat Jericho again to preserve his career with Jericho departing WWE for two years.

5 Triple H

The rivalry between John Cena and Triple H kickstarted in 2006, and they headlined WrestleMania 22 with Cena's WWE Championship at stake. This was one of the first instances, where the crowd was against Cena.

They had an entertaining match, and Cena registered a clean win over the Game. Cena and Triple H touched base several times at WrestleMania 24 in a triple threat match with Randy Orton for the WWE Championship, and the Game defeated Cena to remain as WWE Champion at Night of Champions 2008.

4 Shawn Michaels

John Cena and Shawn Michaels were the reigning World Tag Team Champions, and that didn't stop them from battling for the WWE Championship at WrestleMania 23. They had a good match, and Cena forced HBK to submit to the STF in a successful title defense.

RELATED: Shawn Michaels' 10 Most Random PPV Opponents

They topped their WWE Championship match weeks later on the April 23, 2007 edition of Raw in London, England. Michaels got his revenge by winning the rematch, but he failed to beat Cena for the WWE Championship at Backlash 2007 in their fatal-4-way match.

3 Kurt Angle

The rivalry between John Cena and Kurt Angle is one of the most underrated feuds in the Ruthless Aggression Era. Cena and Angle briefly feuded in 2002, and they clashed in 2003 with Angle defeating Cena at No Mercy 2003.

The height of their rivalry was in 2005 when Cena and Angle slugged it out over the WWE Championship. The Olympic Gold Medalist did Raw General Manager Eric Bischoff's dirty work and Cena and Angle squared off over the WWE Championship at Unforgiven, it culminated at Survivor Series 2005 with Cena retaining the WWE Title.

2 Randy Orton

Randy Orton and John Cena's rivalry in the PG era was breathtaking, but their feud in the Ruthless Aggression Era was just as good. They finally feuded in 2007, and Cena defeated Orton in their WWE Championship match in the main event of SummerSlam. Things got personal in their rivalry when Orton attacked Cena's dad.

Nevertheless, Orton beat Cena albeit by disqualification at Unforgiven, which was going to set up their decider at No Mercy. Unfortunately, Cena sustained an untimely injury which forced him to relinquish the WWE Title. The Viper was the beneficiary as he became WWE Champion, and Cena was unable to dethrone Orton for the WWE Championship at No Way Out 2008 and WrestleMania 24 after he won the 2008 Royal Rumble match.

1 Edge

John Cena's feud with Edge dominated 2006. This is one of the greatest feuds in WWE history, and they were evenly matched. The Rated-R Superstar cashed in his Money in the Bank briefcase at New Year's Revolution, and he beat Cena for his first WWE Championship.

Cena regained the title three weeks later at the Royal Rumble. Their chemistry together was brilliant, and they traded victories at SummerSlam and Unforgiven. Cena's 380-day reign as WWE Champion was remarkable, and the feud between Cena and Edge made Edge a main eventer.