(Imo)Kakuzu, hidan, probably deidara... although maybe evil isn't the word..sasori... although that one might be debatable. Obito wasn't really "evil" nor was oro really, as he probably would of made a move in the war arc if he was... oros more of a sociopath imo
Deidara was already dubbed as a terrorist since he was bombing different villages before his induction into the Akatsuki but to me Oro is a toss up he can be considered a sociopath but at the same time he a murderer due to the lives lost in his experiments he casually throws life away if he finds it meaningless which is pretty evil if you ask me