>>55929036Picrel.
Seems hitting only lowers enjoyment, not affection. There is no benefit to lowering enjoyment. You want it higher, so you can then convert it into affection by petting.
It looks like the only way to lower affection is to trade the Pokemon away, which resets it to 0. But then if you're its OT, it brings it back if you trade it back. If you trade it away and you aren't its OT, any affection you had on it is lost. Transferring through Bank does not change affection. --Which makes me think, if you want to un-affection a Pokemon you're the OT of, it might work to trade it to another game and then use Bank to return it to the original game.