Nope. Genocide is the hardest, as circa somewhere around v7.2 it became essentially impossible to beat. It isn't IMPOSSIBLE impossible, apparently, but it is very close to being so.So the pacifist ending is the hardest? Since you can't kill
I wouldn't exactly call this game as a whole "hard" either, I would rather call it "bullshit" first. The only "difficulty" in it is whether or not RNG screws you over.