No, subliminals are not evil unless they are created with evil intentions with bad affirmations on them.
Subliminals by themself are just a tool you can use to reprogram your subconscious mind. I would suggest however you make sure you know what the affirmations are.
Any good subliminal maker is going to give you the full list of affirmations you are listening to, if they do not for some reason I would not use it.
Subliminals can be used for evil if created by someone with harmful intentions. Which has been done on YouTube before.
You’re installing new beliefs and programs in your subconscious mind so be careful what you are listening to.