#2 Brock Lesnar (2002)
Brock Lesnar had possibly the greatest rookie year of any Superstar in history. He won the King of the Ring tournament in 2002, by defeating Rob Van Dam in the finals, which earned him a shot at the WWE title. Brock never looked back since then, as he went on to put down The Rock at SummerSlam 2002 to become the youngest WWE Champion ever. He headlined WrestleMania 19 with Kurt Angle and won his 2nd WWE title at the event. Lesnar left WWE in 2004, following his loss to Goldberg at WrestleMania 20.
He came back to WWE in 2012, following a dominant UFC stint. Lesnar has since become a mainstay in WWE and has won the top title on several occasions. He recently lost the WWE Universal title to Seth Rollins at SummerSlam 2019.
Also read: 5 big questions SummerSlam left us with
#1 Stone Cold Steve Austin (1996)
After a short-lived WCW career, Stone Cold Steve Austin came to WWE as The Ringmaster. The push that was supposed to be given to Triple H, went to Austin after The Game was punished for being a part of the infamous Curtain Call incident in Madison Square Garden.
Austin defeated Jake "The Snake" Roberts in the finals and gave possibly the greatest promo in WWE history. He soon got into a rivalry with WWE owner Vince McMahon, and was primarily responsible for WWE's triumph over WCW at the end of the Monday Night Wars. Austin was inducted into the Hall of Fame in 2009. He has made several appearances since then and was recently seen celebrating with WWE legends on the Raw Reunion episode.