Mad Hippo, mostly because of his size.

I agree and because he ate a rock like a piece of candy

Oh gosh, he’d love to eat some Jennamite!

Some ACTUAL rock candy!

Yes invite him to omashu

This is a pretty unfair matchup. The Boulder's second hardest fight was with the Mad Hippo. While the fight with Fire Nation Man was just a joke

... Which Fire Nation Man XD?

Mad hippo ofc

one of the earthbenders easily kick him out of the ring as soon as he get in

@BubblePop205 The one from the Earth Rumble in The Blind Bandit

Oh I thought you guys meant an actual angry hippo at first LOL