Is there an antonym for "mentor"?

If "mentor" describes someone that you learn important lessons from, and you are intentionally developing yourself towards their example …

What would an appropriate word be for someone that demonstrates to you what not to do, and that you are developing away from their example?

The closest example dichotomy I can think of is hero v, villain.

Edit-
Perhaps a better word for comparison is "role model"- in that you may not know them personally, but you are actively pursuing their example. The antonym I’m looking for describes someone who you do not want to be like- however this does not necessarily mean that they are a bad person, so these terms don’t seem to fit;

https://www.powerthesaurus.org/role_model/antonyms