Like, seriously, I have had a few people talk about how my fiancé wasn’t conventionally attractive, but he’s attractive to me :)
Plus, he’s good to me, and I don’t date for looks. I’ve had conventionally attractive exes too who have been horrible people, so…
Tell them that they’re ugly and that their partner is ugly. Don’t expand on it, don’t debate, just leave them at that. I’ve found that doing that really fucks with people. That, smiling, and staring at their foreheads, though not altogether because then you look like a jackass. It needs to be subtle and honest.