I would like to clear something up here that I think is a misconception.

Hendrickson is an FBI agent tracking a criminal who he believes likes to torture people to death. This makes him someone who is doing his job.

To him, Dean is a bad person. A monster.

From his pov of that of someone outside the hunting subculture, his position is morally and ethically correct. The only thing wrong here is his information.

He isn't a villain.

He is an antagonist.