You read the title. For me it would be Necron from Final Fantasy IX. I mean, I would expect Kuja to be the final boss and possibly have a second form (like all good final bosses), instead, some random god-like monster appears with absolutely NO REFERENCE to him anywhere in the story up to that point and is like: "I'm Rick James Biatch! Phear me! Die Punkz!" And so I pummel its @ss and say, 'where the frack did he come from?!'
Anyone else have similar feelings?