Most anime protagonists are decent folks. Maybe they make some mistakes or bad decisions, but they mean well. While these kinds of main characters are common, they're not universal. Some main characters are cold-hearted, cruel villains.
Anime with villain protagonists allow viewers to adopt a perspective outside the norm. These anime ask viewers to empathize with characters who abuse, torment, and even murder others. This can be a disconcerting experience, but it can also be a great mental exercise. Maybe the character is hellbent on world domination, maybe they're seeking revenge, or maybe they just don't know how to handle a failed relationship. No matter what, they're doing something wrong, and it's the antagonist's job to try and stop them. Sometimes, these evil protagonists can even make for the best villains of all time.
Vote up the villainous main character who's compelling enough to get you rooting for them... or at least invested in their story.
No list of villainous protagonists would be complete without Death Note. The series features Light Yagami, a young, diabolical genius who uses a magical notebook to murder scores of criminals. However, he eventually gets so swallowed up by ambition that he forgets his own morals and starts killing innocent people just to avoid getting caught.
Death Note poses an important question: Does any one person have the right to decide who lives and who dies? Then, it answers that question with an emphatic no. Light's actions are clearly wrong, and what's fascinating is that we get to see what leads him down such a dark and terrible path.
Alucard of Hellsing Ultimate is a vampire whose job involves hunting his own kind. In another series, a character like this could easily be an anti-hero or even just a hero, but that's not the case for Alucard. Alucard didn't become a vampire hunter for anything resembling moral reasons – he does it because he thoroughly enjoys murder.
Not only does he viciously slaughter vampires, he also kills humans. He shows no mercy and delights in ending lives. He softens up a little as the show progresses, but he's still very much a villainous protagonist.
Lelouch Lamperouge of Code Geass is the exiled prince of Britannia, a fictional empire that is attempting to dominate many other nations, including Japan. Lelouch leads the charge to take down the empire and free Japan from its grasp. In some series, this would have been played as heroic behavior... but not in Code Geass.
Lelouch is willing to lie to his followers, ignore promises, and throw people under the bus in service of his goals. With his dark cape and his cruel, piercing gaze, he even looks the part.
Elfen Lied's Lucy has a good reason for her villainy. She's a special breed of human called a Diclonius, and her status opens her up not only to severe interpersonal and societal discrimination but also to being experimented on and tortured by the government.
Traumatized by her experiences, Lucy starts murdering with abandon. Not only does she kill the government officials holding her captive, she kills her childhood friend's father and sister out of jealousy, and racks up other random kills. While she does eventually begin to feel remorse, her merciless killing and her tendency to torture her victims do paint the grim and bloody picture of a villain.