This character is a villain.

A villain is an "evil" character in a story, whether a historical narrative or, especially, a work of fiction. The villain is usually (but not necessarily) the antagonist, the character who tends to have a negative effect on other characters. In some cases villain might be friendly with the main characters, or even BE one of the main characters (more common in grey morality settings).

A character may start as a villain or hero and later switch to the other side, this trait should be used in either case.