I know you're hurting. I know you can't express your feelings, and it's killing you inside. I know what you're going through. But there is no need to lash out. You can't imprint your pain on people by hurting them. All you are really doing is hurting yourself more.
One day, you will look back on these years, and you won't see your pain. You will look back and you will think to yourself, "Why did I act like that?" You will look back and see all the times you lashed out at others because it was easier than letting them get close enough to you to figure you out.
We all have a purpose in life, and that is to make the world a better place. We each make the world better just by being. But when you start to make the world ugly, you can't save yourself. You aren't becoming any better by releasing hate, if anything you are just becoming every flaw you see in the mirror.
And the person you picked on? The one you called ugly, or fat, or said didn't understand anything? That person? In ten years, they will see you on the street, and recognize you not as the bully who made their life miserable, but the person who taught them to persevere no matter what others thought. In the long run, you aren't hurting them for more than a few days at most. You are the stubborn obstacle they have to hurdle over on their way to success.
As for you, you will spend your whole life as the small petty person who puts others down to make herself feel better.
Because you can't grow out of pettiness, it just doesn't happen.