Alatreon the Ass Wiggler

The Final Final Boss, Alatreon is the toughest boss in the game. He's online-only, like Jho, but you can't trap him, so you can't capture him. Or hold him down to hit him. You don't get base camp supplies. He changes elements during the fight. And he will two-hit you regardless of your armour.

He's a gigantic hassle (for us common folk anyway) but he's a huge badass. For the most part.

And then sometimes he just decides to wiggle his ass at you. I'm not even kidding. It's some attack where he tries to hit you with his tail, but what he really does is spread his legs and lift his ass and wiggle it around and look back at you like "OH HEY THERE."

It's more than a little distracting in the middle of a life-or-death battle with the final boss.