Orochimaru by far. His motivation was pure self service. He wanted to amass as much power as he could because why not? And when he gets a little bored, just start a war between two villages. Or **** with the Akatsuki a little bit.
Everyone else had the whole "I'm doing the right thing, you just don't see it yet" attitude. Their causes were noble but their means were ****ed up.
And Kaguya was just...idk. She didn't have enough of a back story for me to really consider her a villain and she had no personality. She just felt like the Juubi to me, some mindless beast destroying things and wreaking havoc for no reason other than just that's what she does. At least Orochimaru had a ****ed up life story and was explained to always be a little on the psycho side.