He wasn't killed here's the statement of the Reunion Files of the "last" battle a translater made:
"It's said that Cloud was outmatched when it came to the fight with Sephiroth.
Sorry everybody who thinks that Cloud was almost on par with him: he wasn't.
Even worse for Cloud, Nomura said that Sephiroth didn't sweat during the
entire fight and never exerted himself. In other words, he wasn't even trying
hard. Cloud on the other hand was clearly giving it his all and was described
by the book as exhausted by the time the battle was nearing its conclusion."
He never "summoned" a Meteor, The black materia's purpose was to pull celestial bodies tword it (in a TK manor). It never said he couldn't use it on smaller objects.
They are pretty equal.
Going by cutscenes and FMVs, they both showed to: Fly, teleport, create illusions, TK people and objects, use magic naturally.
The Light of Judgement isn't an issue, because of the huge barrier(created around the Crater), and intangibility.
Kefka is more powerful magically, but this is countered by Sephiroth's superior speed and physical strength.
Sephiroth have more experience in direct combat, but Kefka have some dirty tricks.
I don't know who would win.
Whoever you likes more, probably.