.....Well, I THOUGHT what I beat was the last boss.
I beat the After Story a few days ago. True last battle was awesome. Now I'm doing New Game+. Heh, I went straight for the Infinity difficulty without thinking about it twice (and this is despite having only beat the regular game on Normal). Man, do those enemies kick your ass in this mode. I'm still enjoying it a lot, though. So far I'm taking it slow again (right now I'm just doing the new side-quests for the first world), but rest assured, I WILL see this thing through to 100% completion....