Hating yourself is a result of insecure attachment (and additional traumas from peers, the dominant culture and toxic ideas about bodies and success).
You don't hate yourself because something is wrong with you. You think something is wrong with you because you were taught to hate yourself. (Aka no one knew how to teach you to love yourself)
The first step to self love is grief, not improving yourself. It's opening up yourself to grapple with the pain present in the story of your attachment relationships. And seeing yourself with new eyes. You weren't ever unlovable, no part of you was. But you did likely have caregivers who didn't know how to love you in the ways you needed. (And also hated themselves).
Healing now is about radically loving and accepting yourself exactly as you are. And as you do, you'll be amazed at how many things you can love about yourself. So so many.