free trial villain
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?"
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?"