Its hard for me to consider some abstract embodiment of evil or something supreme faceless "behind the scenes" monster to be an actual villain. They were just standard "evil" incarnate monsters. To me, things like Chaos and Zeromus shouldn't really count

I haven't really played 2, 3, 11, or 14

Haven't beaten 5, 10, or 12

Soo my pickings are slim, and my exposure is probably not valid enough to warrant a justifiable opinion