No, the Kudan fight. Like, wtf. Once you split into two, he can one-shot you from full health at any time, and then you lose. And I don't have enough healing items, and the game doesn't let you buy more. This is the most poorly designed shit fight I've ever seen. Yes, I'm raging. You can double debuff his attack, but he can just negate the debuff and double buff and then still kill you in one turn.
Edit: Oh and I just learned that when you press 'retry' or 'restart' it doesn't re-instate the items you used. So now I have no good healing items at all, and I saved without realizing. What a horrible way to end the game.
Edit edit: So turns out the dev put a single enemy unit in the area which gives a lot of XP. So you can grind that. Still an awful section, but at least it's not a soft lock.