10. Big Show
The early days of the Attitude Era were all about major names jumping from WWE to WCW, but by early 1999 the tide had well and truly turned. Superstars were starting to move in the other direction, and one of the first big time players to head to the Vince McMahon-captained promised land was the man who eventually became the Big Show; Paul Wight. Billed as The Giant in WCW, Show won the WCW World Heavyweight Championship in his first match, albeit in a real schmozz of a disqualification finish. WCW! Booking nonsense aside, it was clear that The Giant was a once-in-a-lifetime prospect, a humongous man with incredible athleticism and obvious ability to function as a babyface or a heel.
Boy oh boy did that ability get ran into the ground.
What does all this have to do with The Undertaker? When Big Show made the jump he did so with a chip on his shoulder, a chip salted with main event history and the safety of being immediately thrust into the Vince McMahon/Steve Austin feud. Big Show allowed all of the attention to go to his head and acting like the proverbial dog's, talking down to other wrestlers (also literally, what with the height) and generally showing off. 'Taker wasn't going to stand for this, and Show was eventually brought down to size.
Which was all good and well, as Undertaker and Big Show went on to have approximately 345945 feuds over the next couple of decades.