My horse used to lunge at horses walking down the barn. We left a soft broom outside his stable, and picked it up every time we walked past. One whack with it totally took him by surprise and he stopped doing it when he realised there would be an instant consequence. Now he licks people walking past, and very rarely puts his ears back!
Yeah I had a horse and he was also aggressive and a few slaps he soon got the message and it will sort him out.I know it sounds harsh but I agree that the herd leader would do the very same.Its better do it now rather than later when he could injure you or someone else.Dont be afraid cause they can sense that and even try to bite you after you have slapped them as they always try to get there own way and be the leader with in many ways is a bad thing. Good Luck😀
Not a popular or PC opinion, but biting is a serious offense. My friend had to have stitches when a horse randomly
Lunged at her chest. Hit him on the nose with an open palm and say "NO" very loudly. He will probably be startled and go to the back of his stall to pout. But biting is no joke. Never fist, open palm like a slap. Do not tolerate this behavior. The herd leader sure wouldn't and he'd be double barrel kicked in a flash.