The greatest compliment is validation that I'm doing well in an area I really believe in. When I think of you, I think "courage", I can count on you to be real, you are intelligent. Being told that I am trustworthy is a big deal. Invoking potential also feels good, as I found out today: you have so much energy inside, it's all in how you use that passion.
Being told that I am only pretending or do not follow my own ethical values hits extremely hard. If it's true, you have the salt in the wound factor: the discrepancy was certainly the most emotionally demanding and troubling thing on my mind before anyone confirmed it.
Another bad one is having your future predicted, which "There will be no place for you in the world to come" falls under. You will never experience love. You will always be alone. You'll come crying back to me when it doesn't work out.
The worst insult I can imagine, period? Being called boring by somone you have opened your inner world up to completely.