Definitely not Madara.
Why? He is literally dead. He is a relic of the past, and really all he has done is through other people. He didn't kill anyone we know, he hasn't defeated anyone we know, and he hasn't caused any major damage.
Probably not Orochimaru.
Why? What kind of reasoning for being evil is KNOWING ALL JUTSU HERRRRRR? Imagine when he gets the Rinnegan... NOW I CAN LEARN C-RANK KATON JUTSU, YES!!!!!!
No.
OBITO
The man who caused the protagonist all of his suffering, the man who took over Kurama and ravaged the village, the man who now summoned the Juubi, the end, the god of all creation, and the man who lost faith in humanity...
btw its almost disrespectful to all of the villains to put someone like Sasuke on their level.