Much Like Jeff Jarrett, the first wrestler on this list, Psycho Sid Vicious got big pushes from two wrestling promotions, won multiple World titles, and was a one time member of the Four Horsemen. This is tough to bag on a guy who snapped his leg in many pieces due to the mismanagement of that company, but Sid never really lived up to the pushes he got from WCW or the WWE.
More than that this guy was a real asshole, who got fired from WCW once for an ugly incident where he stabbed Arn Anderson with a pair of scissors.
Sid seemed to have it all, a great look, and lot of charisma with the fans, but he was terrible on the mike and had a very bad attitude in the locker room. I can remember fans cheering loudly when he eliminated Hulk Hogan in the 1992 Royal Rumble, eve n though the WWE edited out that reaction from future video releases of that event.
Some of his career was hurt by others, teh WWE apparently screwed him on the buildup to Wrestlemania 8, and Papa Shango (aka the God Father) apparently missed a cue to break up a pin in his match with Hulk Hogan at that event.
Even though he won the WWE title twice, and the WCW title twice most of Sid's career was a disappointment. Seriously they put this guy in the four horsemen? What the hell? That never worked, and given his size and look I really wonder why he was never in a long feud with the Undertaker. The two did face each other at Wrestlemania 13, but a longer feud could have and likely should have been developed between the two.
When he would up back at WCW, the company mismanaged him again with a ridiculous winning streak claim that really showed the incompetence of WCW management. Throughout his career it seemed fans were willing to get behind Sid, but either he or the promotions he worked for were able to capitalize on that.
In a lot of ways he laid the ground work for Steve Austin's anti hero character. Sid did a lot of things that would be classified as a heel, but still the fans liked what the y saw in him. It is a shame that two wrestling promotions were unable to find a way to make that work.
Of course his backstage difficulties are the likely reason why Sid was never truly a huge star in pro wrestling.