That One Boss/Other Games

This section is for bosses from games that don't fit any other typical mold: gamebooks, visual novels, tabletop RPG's... even fictional bosses are allowed! The only criteria, as usual, is that they're noteworthy for being ridiculously hard!

Other Examples

 * The Chaos-Master from the 11th book in the Lone Wolf series of gamebooks. It's a hideously hard fight if you don't bring the Sommerswerd along. If you do? Chances are you will die horribly. There's a particularly infamous Let's Play of Book 11 that had the players redo the Chaos-Master fight twenty-seven times before they finally won. It's that hard.
 * Not actually a game example, but in the manga The World God Only Knows, Keima Katsuragi can capture any girl... any girl... with the exception of Yui Goido. He himself notes she is a serious player, introducing a new meaning to Player vs Player.
 * While the final bosses of the Ace Attorney series usually take longer to break than other culprits, the final showdown in Investigations gets special notice for being so long and difficult that there's a save point in the middle of the fight.
 * And here's a song about how difficult it is.