Stop trying. Give up. Make him want to leave you.
Stop telling him things. Stop trying to make him smile. Stop being so responsive when he talks to you. Don't make out with him anymore. Pretend you're very busy. Start talking with other guys, and hanging out with them too.
Pretend you don't care about what your boyfriend does. Act like he can do anything he wants. Don't show him he can hurt you. Show him that his words are meaningless to you. That you just don't care about him anymore.
If he doesn't get worried, then it's because he doesn't care about you. If he doesn't care about you, then I don't see why you're worrying about hurting him by a break-up, since he won't get hurt.
But if he notices you're acting strange, and acts why, then it means he does care. If he asks you why you're acting strange, tell him you don't like the way he's been treating you. Tell him you don't like that he always hurts you, and how he never listens to you.
If after he realizes this, he still doesn't change, then go ahead and tell him you don't want to see him anymore. Doing this is perfect because this way, it's his own fault and he won't be able to blame you. He's the one who hurt himself, by aggravating you to the point where you felt like leaving him. Also, this way it gives him a chance to redeem yourself and hopefully avoid the break-up by making you want to stay with him.