A term meaning a character in a series has only been
evil once (or rarely, twice). But, during that
time they were villainous, they were extremely
evil and heartless to the point that some people would even consider them villainous normally.
Guy 1: "Wait, I thought that person in the series was
evil, what happened to them?"
Guy 2: "They were only
evil during that episode. They didn't turn
evil and kept being evil for the rest of the series. Something happened and they turned good again."
Guy 1: "Oh so they're a free trial villain?"