I find most RPG endings to be lackluster to be honest so it is a bit difficult to single out one that irritated me. Probably FFXIII's ending because it involved a poorly implemented Deus ex Machina that kind of destroyed whatever message the game was trying to make. I mean I've seen games magically resolve crap with ass pulls before but this game had little in the way of any set-up.

I'm really struggling to find another game that was as irritating to me though I am sure there is one, I'm just not thinking straight tonight.