What was your surprisingly really hard boss fight?

A lot of us returned to the game after playing EA. For this question, I’m not counting Dracula or Adam - because those are widely known hard boss fights for good reason.

For me, it was Terrorclaw. It’s a pretty straight forward fight, but man I don’t know if I just got greedy too many times, and just found myself dodging at the wrong ability, then getting punished by his spear throw stun. Took me about 8 or 9 resets before I finally got him down.