Gamers, what’s the hardest boss fight you’ve won?

I play easy games generally, but the Boiling Lizard on B3F of the Golden Lair in Etrian Odyssey IV was very hard for me. He keeps materializing hot scales on the battlefield that heal him. I eventually won, but it was exhausting and took a very long time with a lot of strategy. Thank you especially to Witch’s healing and DoT debuffing circles, Henry’s debuffs and buffs, Max’s status inflictions, and Rusty’s binding.