When you say it that, yes, it sound easy.
However, the vilain in my story is quit...well, I'm not going to reveal too much about them since it be a big spoiler, but I am going to try my best to explain in short their story and why it may be hard to find a balance between their horrible act, and the reason they act that way. (then again, I may look too deep into it, feel free to correct me if I am overlooking).
So, in order:
1) They are a artifical lifeform created by apathic scientifists. (note, none of them are humans, so empathy and those kind of stuff don't apply for them)
2) Despite making sure they wouldn't feel anything, this new lifeform is still able to feel emotion like you and me. So, what does the scientifist does? Do horrible experiment on them that, for the most part, kill them over and over again in horrible fashion. They want to create the ultimate lifeform (



) so they don't want to bother with such useless things as emotions. So they just expect that the newly born creature will just stop "feeling" and just "think". (the newborn ability to regenerate being so good, it's basically a curse for them)
3)Despite the mentionned tortures for countless time, the creature still manage to remain somewhat sane and able to feel emotions. However, as you can guess, they are now pretty **** up in the head. Since among physical torture, they also got inflicted with emotionial torture, which warp their notions of right and wrong and thus, give a reason as to why some of their actions later on are so souless and horrible.
I'm going to stop for now, but tell me if what I descrive give the ground for a vilain who fit those rules.
Also, note that the creature is a shapeshifter who can become litteraly anything and can even change the appearance of others through rather horrible way, so imagine what sort of horrifying scenario a creature like this can inflict to poor innocents.
Eh, not thanks, I don't want to join your...friendly discussion.