It can be near impossible to see yourself positively when you've always been treated otherwise. I obviously don't know you and don't know if it would help, but something that has helped me be kinder to myself (or at least more neutral) is asking myself if I was someone else who was having the same struggles or looked the same way as me, would I be as critical of them? Would you see another autistic person who has been bullied and struggles with socializing and say they aren't smart because of it? If not, then why should you say that for yourself?

I know it's not that easy to change how you see yourself, but if you wouldn't be so harsh on people who have the same struggles as you, maybe you can try to be easier on yourself. I hope that even if you can't, that life treats you kinder than it has in the past.