#3. Brock Lesnar vs. The Rock - WWE WrestleMania 30

"The Rock vs. Brock" was the tagline that WWE used for SummerSlam 2002 - where a young Brock Lesnar decimated The Rock to win the WWE Championship just four months after his debut. There was never any WWE superstar pushed as hard as Brock Lesnar right from the get-go. After the PPV, The Rock wouldn't hold the WWE title for another 10-and-a-half years.
The Rock confirmed on Twitter that there were talks between himself, Lesnar, and Vince McMahon about a potential "Rock vs. Brock" rematch for WrestleMania 30:
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As it turns out, The Rock wasn't able to compete at WrestleMania 31 either. He appeared in the opening segment of WrestleMania 30 alongside Hulk Hogan and Stone Cold Steve Austin. At WrestleMania 31, he appeared alongside Ronda Rousey in a confrontational segment involving Triple H and Stephanie McMahon.
Brock Lesnar, on the other hand, ended The Undertaker's WrestleMania streak in 2014. Lesnar went on to headline WrestleMania 31 the following year, where he lost the WWE Championship thanks to Seth Rollins' MITB cash-in.