My dad: "Useless piece of shit"
My mom: "You are just like your father."
My old boss also once told me to just go and kill myself, like as a joke, but I wish I had
Comebacks for those:
To Dad: "I learn from the best"
To Mom: "And you married him, what does that say about you?"
To old boss: "I bet you will win that race, being in management tends to elevate suicide chances"
"You're cold hearted, you have no empathy". -- My high-school professor (who otherwise liked me) after I made a case that people who decide to keep a child with Down syndrome are not heroes and that they're not more valuable than people who would have aborted it.
"How come you have top grades in PHYSICS but you're so bad at PHYSICAL education?" -- Classmate after I proved how bad I am at catching a ball.
"You're so unkind and isolated that you're getting ugly" -- Dad when I was 10 and I didn't want to hang out with my cousin anymore. I liked being alone from an early age.
"You are mentally ill. You need help" -- My ex while I was 15, in the middle of a panic attack and I refused to get out of school to get lunch.
Comebacks
To Professor: "You're only saying that because if someone heard you saying the opposite, you get fired, even though you believe the opposite"
To classmate: "Don't worry, I have all the time in the world to excel in catching a ball, while you get to learn how to take my order at McDonalds"
To Dad: "I see you're projecting again, is that why you're balding in places you shouldn't?"
Your ex: "Thanks for stating the obvious, now you can go pat yourself on the back for being so helpful /s"