Don't resort to forceful aggression because you'll only make you horse afraid of you. If you go online there are plenty of things about natural horsemanship and other methods geared toward establishing a herd leader type status with your horse. He will then see you as the leader rather than the "enemy"
Go into the paddock ready for war. Airhorn, plastic bbag, anything scary but handheld. He so much as makes at face at you, scare the shit outta him. He'll realize that you're boss, even in his space.
I know someone who deals with horses like that and is very kind and sweet. If you want I can give you her number?
We had this happen with one of our boarders. The horse was put in a round pen away from her buddies, and eventually she stopped being as dominant.
If it's not a medical problem .then I would make sure he respects you on the ground.or he may not whant to be riden because of an saddle fitting problem .or stuff like saddle /bit/or he may need to be chiropratcored .!?
I would carry a whip with you, and when he becomes aggressive wave it back and forth close to the ground to try and keep him out of your face. Try not to show fear, because he will pick up on that and become even more aggressive. You could have him checked by a vet if he gets worse to make sure there is nothing wrong with him physically. I would also wear a helmet when you go out into the pasture just for safety.