I haven't had any exceedingly hard battles on my current run-through...though the first time I got to them, the wall of the temple of the ancients and Jenova-LIFE (Last battle of Disc 1) were real pains...until I decided to over-equip Cloud with Bahamut and Enemy Skill w/ Trine (which is the best E-skill for the first part of the game...until you learn Aqualung) for the wall...and smartly equipped the Water Ring I got in the forest before I headed to the main plot twist of the game...

And, in fact, I JUST faced Proud Clod for the first time (yeah, I suck)...and he didn't seem tremendously hard...just Bahamut, Neo Bahamut, Bahamut-Zero, Ultima, Comet, Regen, Trine, Aqualung, Magic Breath, Meteorain, Tifa Combo, Chainsaw Monster, he's dead...(I think that was the first battle she actually was able to use Final Heaven for me...like I said, I suck...)

The pain was the thing that loaded up the sub...so the 2nd time, I threw the same combo as above at it...much easier.