@Doesitgeteasierthanthis
I need to listen to friends and family that I am good enough and somehow learn to believe it
This is the problem. Have a read about validation. External and internal. Family and friends and this man can all think what they like of you, positive or negative. This isn't about that.
This is about what you think of you, and how you feel you want to be treated. Other people's opinions of you are irrelevant, and as soon as you start to 'listen to' the good ones, you make other people's opinions of you matter. Once other people's opinions matter to you, negative ones matter, too.
You are not faulty. There is nothing wrong with you. Any of us could meet someone who would put us down, make us feel like crap, de-prioritise us, etc. The fact that you met someone cruel isn't your fault, any more than a bystander who gets punched by mistake in a fight. The problem is that you don't walk away when things turn unpleasant. And that's how to fix this. You don't have to 'do loads of work on yourself' (because you're not broken), you don't have to 'listen to what people tell you' (because it varies, for you, and for everybody) You have to take responsibility for yourself. This is just like being responsible for a child. You don't teach a child to work out, with their bully, exactly what they did wrong to deserve the bullying. You don't encourage the child to engage with negative opinions of them, or with meanness. You encourage the child to not take the cruel words and actions to heart, and to not place themselves at the mercy of the bully. Basically, 'keep away from those nasty kids'. This is what you need to promise to do for yourself. Stay away from the mean boy. He doesn't know better than you, or anybody else, about who you are. He has no authority or power or control over you, and cruel behaviour says everything about the perpetrator and nothing about the victim.
Recognising that you are responsible for your own wellbeing, and that you have to look after not just what you eat and how much exercise you get, but your whole self, including the company you keep, how to make yourself feel good, how to make your life just like you want it etc, is a massive realisation. It's up to you. There are no 'rights' and 'wrongs', because there is no authority (other than the law). We can all treat each other cruelly, or kindly, or anything in between, with impunity. And so, as individuals, it is up to us to select what makes us feel good in life, and to de-select what makes us feel bad.
Take charge. He is gone. What would make you feel good today? A walk? A film? A friend? Minstrels? Music? A cafe? A book? Think of all the things in the world that make you feel good. Write them down in a list. Do them over and over, as much as you can, for a week. See how you feel after that week. Do it for a month, and see if life is improving. This whole problem is simply about you learning to choose things that feel good for you. Allow yourself your recovery time. Nurture yourself, and do not leave yourself prey to more ill treatment in the meantime. That's the only work you have to do, and it looks forward. You never have to look back.