I'm not saying Orphan was hard, but I am saying that it's far from the easiest. Maybe I just found some bosses in FF way too easy... I'd say it's on par with most of the bosses I faced. Poison might do most of the work for you but there have been bosses in Final Fantasy games that I have basic attacked + cured my way through. I think that's the definition of easy, personally speaking. But then maybe I'm always overleveled/geared by the time I fight the end boss? I dunno.

Ultimecia is just too easy to be anything but #1 for me.

Also, just realised that Bhunivelze isn't on this list as far as I can tell. I think it took me multiple attempts to beat him, which is more than I can say for most FF bosses.