No. 2: Pandemonium Warden – Final Fantasy XI

Surprisingly the only MMORPG boss to make it onto our list, but with good reason. This Final Fantasy XI boss was so crazy-hard that it made people physically ill in real life. It accomplished this horrifying feat by taking over 18 hours to down, even with a very high level group. After news of subscribers wasting away because of this monster came out, Square Enix fixed it so that the Warden was significantly easier to defeat and would despawn if not downed within two hours of battle. The Warden gets a spot high up on our list for the sole fact that it could affect people’s HP in the real world. And that is damn scary.