Soo.. next Part of Omega: FFVII?

[Mixt]

Cause he is edgy.

While in FFVII he was pretty much just a thrall to Jenova.

Not really.

Jenova had basically been reduced to braindead hunk of meat at that point after being sealed away for ages in a geological stratum and whatever the Cetra did to it.
Sure, the powers were all there, and it was very much alive, but nobody was home anymore.
Then Sephiroth went and moved into the drivers seat so to speak.

Though there is admittedly an argument to be had that Jenova's instincts had some influence, the whole thing with the mind being affected by the state of the body and all that (See also: Person that get's turned into a frog instinctively trying to eat flies)

Why is Sephiroth considered the strongest villain?

I could write a very lenghty post on the matter, but i don't think anyone would even read it.
Certainly nobody ever has whenever the topic came up on any other forum.
It's always "Too long, didn't read" "To many details i don't understand/too complicated, stopped reading less than a fifth of the way through" or something else along those lines.

Also, he's not. That would be Bhunivelze, creator and destroyer of entire universes, even if he never got the chance to act on the latter.