He's the one you don't otherwise handle much right? So he's getting a free ride? Could be some regular, manners-oriented ground work would help. In fact, if you caught him at the gate each night, and instead of feeding, tie him, put the others in but don't feed yet (hearing the feed pan noises might be more than he could take) and lunge him a few minutes, making him go slow, and really demanding perfect behavior, I mean chain under his chin and the works. That you might knock his ego down a notch or two. When he's good, then lead him in and feed everyone. The routine as it is has him over-excited. Changing the routine to something else might help.
We did some of that with Cyn.
He has a LARGE ego, that's for sure. This really has been his only problem. After he's in and eaten, he's calm as a cucumber, doesn't even seem like the same horse.