Im with you Rydia, i had it up to my eyeballs with that freaking wall myself....instantly killing players and when you try to revive them, the wall just killed someone else....if it wasnt for Rydia, id never have beaten that wall... thank god for green haired women!

well dark bahamut was hard because i was SERIOUSLY under leveled. but zeromus was quite hard as well, because i was underleveld again. i didn't know about dark amtter at that time so big bang did a lot

I usually get fucked up by the Wall. Rubicante is pretty hard if he starts using his strongest attack a lot. But both of them are dwarfed by some of those bosses in the Lunar Palace, including, and especially, Zeromus. Holy hell, hardest FF final boss ever. (Well, after X-Death.)

it was totally zeromus and evil wall

I've found this game to be the hardest I've played. I've done several runs... and not completed it.
The first time, I found Baigan really hard :S don't know why
Second time, I lost to Valvalis.
I'm going through it now actually, managed to get up to Zeromus and I'll fight him later.

Bosses I didn't find hard (which I've heard are tough) are Ogopogo, Evil Wall and the Four Fiends (beat it first try).

Zeromus wasn't the toughest boss EVER (try K.Rool in DKC 2), but he was annoying.

I had a lot of trouble with Evil Wall in the PS version (never completed it because of him) but I was young at the time. In the GBA version I found him very easy, beat him on first try.

The hardest boss for me would be Zeromus. Why people want Rydia to live for the fight, I do not know. I desperately needed the Curajas to heal after Big Bang, if I had to deal with his counter-attacks as well I would be dead meat for sure (so I just left Rydia dead/KO'd). I was at mid to high 40s when I beat him, IIRC.