#1 The Rock - WWE Champion (1999)
During WWE's Attitude Era, one of the biggest rivalries (and later alliances) was The Rock and Mankind. At Survivor Series 1998, The Rock won the vacant WWE Championship in a match against Mankind.
Following that, the pair carried on feuding, and Mankind won the WWE Championship from The Rock, 50 days later, on the December 29th episode of RAW in a no disqualification match. This only seemed to add more fuel to their rivalry, and another championship match between the pair was set for just under a month later at the 1999 Royal Rumble.
A top AEW star just called one of his colleagues 'spoiled' and 'narcissistic' HERE.
The match set for Royal Rumble was an 'I Quit' match, and became known as one of the most intense matches of its kind in WWE. It was one of the subjects of the 1999 wrestling documentary Beyond the Mat, where the wife and children of Mick Foley were seen upset at the action and left the crowd.
After The Rock hit Mankind with multiple chair shots, audio of Mankind saying 'I Quit' was played, and The Rock was declared the new WWE Champion.
However, the WWE Championship passed back and forth again between the two, with Mankind winning the title back two days later, and The Rock becoming the WWE Champion for the third time in April of the same year.