Toshio Ozaki

Toshio Ozaki is one of the main protagonists of the anime/manga Shiki. Despite being one of the show's main protagonists and being seen as justified by many, he commits morally ambiguous acts during the second half of the show that could be considered villainous. The show itself is purposely written this way to make its audience think about morality and so whether or not Ozaki is a villain is left up to the viewer.

Moral Event Horizon
At the start of the show Toshio is a hard working and strong willed doctor of the Ozaki Clinic. As mysterious deaths begin plaguing the town he works hard with his good friend Seishin to discover the cause of them. After a series of traumatic events Ozaki comes to discover that the village has been invaded by undead creatures that feed off of humans called the Shiki. Ozaki is helpless as the Shiki take over the village and eventually even his wife falls victum to them. Ozaki does not tell anyone that his wife died and instead keeps her body in his private lab. Due to everything he experienced from the Shiki, Ozaki comes to see them as monsters and has no empathy for them. When his wife comes back from the dead Ozaki commits an act that can be considered his Moral Event Horizon. With his wife tied to a table he begins doing painful experiments on her to discover the weakness of a Shiki. The woman screams in pain and refers to him by name, showing that his wife is still the same person but Ozaki continues his experiment not caring. It all ends with Toshio driving a stake through her heart and killing her. Covered in her blood Ozaki asks Seishin to help him clean up but Seishin leaves the hospital in horror. It is at this moment that the friendship between the two is severed and Ozaki begins down the path of vengence.

The Hunt
Ozaki's attempts to tell the villagers about the Shiki invasion fail at first but eventually he gets the upper hand and the truth about the Shiki ends up being revealed to the entire village. This begins the hunt to kill every last Shiki in the village. Despite the Shiki's need for human blood to survive and villainous acts they still have the emotions and mental abilities of normal people. Though some of them such as Tatsumi are melicious the Shiki are not all evil and simply feed to survive. Despite this Ozaki orders them to be inhumanely executed with no mercy and treats them as if they were complete monsters. Though these things are done to protect the villagers they are so horrifying and Ozaki shows such little remorse that some view him as a villain. Plus when the villagers do things that Ozaki is against (such as killing people being controlled by the Shiki) Toshio does not do much to prevent it. When he sees Seishin trying to escape he allows some of the hunters to  go after his friend as he knows that he is now working with the Shiki. After the entire village is soaked in blood from the hunt a fire breaks out and Ozaki tries to save it. This does not work and in the end Ozaki and the surviving humans flee the village. As he leaves Ozaki ponders whether or not he was sucessful due to the village being burned down. Little does he know that Sunako and Seishin escaped so whether or not Ozaki truly won is entirely left up to the viewer.