The only reason Cloud stands a chance is because Sephiroth wanted to prolong Cloud's suffering as much as possible, which backfired when Cloud's most powerful limit breaker came out.
The first time he beat Sephiroth was against a mentally exhausted Sephiroth who had already defeated a powerful foe, and was blindsided by a sword to the back, and even that didn't defeat him, he had to bleed out for like a half hour out of a wound that covered the majority of back, and even then Cloud BARELY was able to overpower him :P
The second time was when Sephiroth had already been defeated by several people, and where Cloud and Sephiroth were in a place where Sephiroth's enormous speed, strength, durability, and reflex advantage was taken away from him (aka the Lifestream).
And the third time Cloud was all but dead, and had it not been for Zack and Aerith saving his sorry butt throughout the last 20 minutes of the movie, would have died instead of gaining his limit breaker!
Thor one shot him, Ghost Rider one shot him, WBH one shot him, Dr Strange one shot him, Wally West one shot him, Doreen Green erases him from existence and solo FF universe for the lulz
I will debate Sephiroth against Thor any day of the weak, and I already debated Sephiroth against WBH, and only lost that match by a single vote. Doctor Strange is also heavily debatable. Wally West obviously would win, and Doreen Green is unbeatable, so there's no shame in that.
Thanks for reading,
if ifs and buts were candy and nuts...we'd all have a merry christmas.
Cloud, I say.