Originally, the villain hadn't really thought of killing the protagonist officially at first. Even though the man had accidentally killed his wife, he knew that the man was innocent. So he decided to curb his anger and continue to live away.
In his view, if he didn't see the man's face, he wouldn't get angry anymore.
Things only went wrong when he had to visit the zombie dwelling with others to sign the peace treaty with the zombie king. Everything was going well, and he was just about to return home when he overheard the protagonist talking about how he wanted to make everyone his servant, even the people of different races.
In reality, the protagonist was making a sarcastic comment and joking with one of his zombie servants, but the villain didn't know. The latter thought that the man was serious and became angry.
