If a friend of the opposite sex calls you ugly in front of you, how can you severely refute him?

I think you should find out his purpose first.

Because if you are a same-sex friend, you may be disdainful or jealous.

But if he is a friend of the opposite sex, there must be a cause and effect for him to say so.

If it is intentional, in fact, the best way is to ignore him, because ignoring him is equivalent to simply looking down on him.

No matter how ugly it is, being ignored is the most humiliating thing.

If it's not intentional, it should be just a joke, so there's no need to care. Just kidding, reply.