For computer game I would have to say Summoner, clumsy game and well the graphics was kinda.. cubish and well not at all that fun, and the level up bit was kinda pointless.. Too much of Diablo, too little of the good diablo bits and well the setting and atmosphere were kinda dull..
There are probably worse, Like Final Fantasy 7 (if you can call that a rolepalying game) and that Japanese influenced one with a cyberpunk.destroyed earth future thing.. Really awful..
For the pen and paper.. Hmm, Twilight 2000. No roleplaying really, a matter of destroying enemies and crappy system and unrealistic making of characters and the combat system made a couple of friends and myself close to fall weeping!
Merp is also a bad example, too many lists, referance tables and stuff that kills the flow...