Not even close.
As we learn in Nibelheim, a bit of doubt and then some books can make Sephiroth totally lose it.
Demonstrating a very weak psyche.
While in the UOG, it says he controls Jenova with his mind.
Yet we're told specifically in the game to control or change someone's appearance, voice and mind is "the power of Jenova."
Sephiroth, on the other hand, never showed this power once.
As clearly depicted, Sephiroth went evil for "his mother". Yet he learns she is not his mother. And that his entire motive for killing and being bad is non-existent. So he takes her over with powers he never showed or was stated to have and continues on his way, being an even less developed villain than Bowser.