There are the following possible responses:

Fight back with humor or self-mockery, such as "boiled water is also water, so don't underestimate the power of water" or "plain appearance is to leave room for others' imagination".

Use idioms or famous sayings to express your attitude, such as "You can't judge a book by its cover, but the sea can't be measured" or "Beauty is a gift, and wisdom is a virtue".

Use facts or examples to prove your worth, for example, "Although I am plain-looking, I have many advantages and talents, such as …" or "Look at those successful people, how many of them win by their looks?"

deal with it in a cold or indifferent way, such as "what did you say? I didn't catch it "or" Sorry, I'm not interested in discussing this topic with you ".

I hope this information will help you. ?