Vader's a prime example of a guy the WWF missed the boat on. He was a beast in WCW but politics (i.e Shawn Michaels) killed his chance to rise to the top in WWF.
Vader was supposed to win the WWF Title at Survivor Series 1996 (it's why the December In Your House that year was subtitled It's Time, after Vader's catchphrase) but Shawn Michaels didn't like him so he politicked his way out of it. At least according to Cornette in his most recent Kayfabe Commentaries interview.
Vader would be an awesome addition to WWE if he was in his prime nowadays. A big man who is somewhat agile and can do flips off the top rope and stuff (and has a cool finisher.)