Thanks for the comments guys. I’d have replied earlier but when I try to login on my phone it just loops me back to the logon page

I’m really surprised that I have to defend Sephiroth and everyone is defending Vayne.

I enjoyed FF12 and hunting Marks and Espers but I just found I had very little motivation to go after Vayne and defeat him. Why should I hate him, why should I care?

As for Sephiroth, how can you say he’s not a great villain. From his sanctuary at the North Cave he broke Jenova out of Shinra building killing many, impaled the Midgar Zolom, murdered a key character and was happy to summon meteor and cause untold damage just to gain godlike powers for himself. Or his projection of himself did in some cases.
BUT I haven’t played any of the spinoffs. I’ve heard that they attempted to explain and expand an already complex story and may have diluted Sephiroths character as a result.
Some of the people arguing the case for Sephiroth have done it far better than I could.

In regards to some of the other comments I think a lot of the villains in the background may have done some great villainous deeds but they’re just too anonymous for a lot of the game. The NES villains fit here although to be fair, the NES didn't have too much to work with compared to modern games.

Perhaps I should be blaming the storyline rather than the villains. I guess I enjoyed Kefka and Sephiroth so much because you’re constantly pursuing them and battling them throughout the game unlike say Ultimecia who you only find out very late on is the puppet master. She may be there possessing other sorceresses but you can't see her. You don't have a tangible target to hunt down.
Golbez is also great because you constantly purse and interact with him through the game, it just turns out he’s not the ultimate villain.