#1 Raven - The Seven Deadly Sins
Raven is arguably the biggest superstar to sign with WWE who had a miserable run and was under-utilized in every way.
Raven was easily the best promo-man in ECW history, and although under-utilized in WCW, his mid-card booking there was nothing that he couldn't bounce back from. However, when it was all said and done, Raven's treatment in WCW was main event level when you compare to how he was used in WWE. Raven would mostly compete on WWE C-shows like Heat and would only ever wrestle in Hardcore matches on RAW and SmackDown, when he wasn't used to put others over.
After being a background player during the Alliance invasion in 2001, it seemed like WWE may be about to do something very interesting with the former ECW Champion in 2002. Raven suggested to the management that he take on a gimmick of 'The Seven Deadly Sins', where he would take down members of the WWE roster for breaking them. The gimmick briefly made it to TV on Sunday Night Heat, where he demonstrated the likes of 'Greed'.
As he was feuding with Matt Hardy at the time, apparently there was a plan for 'Lust' and 'Envy' to be brought into it and having Lita side with him over Hardy. The whole angle was dropped before any of that could materialize however. Raven instead reverted to his previous losing ways before being released by WWE in early 2003. Thankfully, he revived his career for a few years in TNA and even had the company use a lot of his ideas.