12 WWE Monsters That Failed
7. Heidenreich
One of several wrestlers to spend time on the chalkboard as a possible WrestleMania opponent for The Undertaker, Heidenreich's muddled WWE run featured a spell as a dangerous heel but was bookended by two credibility-sapping babyface stints.
Appearing on Raw in 2003 as a slightly unhinged friendly face referencing a never-paid-off 'Little Johnny', Heidenreich did little of note before returning on Smackdown as a heel alongside Paul Heyman.
As others can attest to, just being a 'Paul Heyman guy' doesn't guarantee greatness, and despite his increased psychopathy extending to assaulting planted members of the crowd and reciting terrifying poetry, it was apparent he was sinking fast.
The inevitable Undertaker feud yielded poor high profile matches at both the Survivor Series in late 2004 and the 2005 Royal Rumble, and even briefly sucked in Raw's equivalent Kane/Snitsky feud for the planned WrestleMania 21 tag team match, but the idea was ultimately dropped at the request of 'The Deadman'.
Out of juice as a heel, Heidenreich turned face and ultimately wound up as a Hawk replacement in a woeful 2005 reboot of the Legion of Doom. When that stint predictably cooled, he was released, and has later admitted suffering from severe depression as a result of his WWE tenure.