The boss spawns in a very small arena, has tons of hp, does tons of damage, and most of his attacks move too quickly to be reacted to. The arena's bouncy walls are easy to bump into and immediately get flung into him and it seems like he randomly scales the damage required to kill him to significantly higher than Moon Lord despite being directly after. Doing some research, I found some older videos where the arena was larger and a wiki that mentioned a damage buff for the first time kill of this fight, this could have been changed but I don't know.
Am I missing something or do I just suck?