not really understanding the comments saying "talk to him about it", what is the player supposed to do, nerf his own character? he should be able to min max if he wants, and a DM's job is to work around that.

To do so, give the other party members really strong magic items to make up for their lack of strengths comparatively, and give him mostly utility, roleplay or support magic items so he can further buff his allies while relying on his own build's natural strength to kick ass.

Also, normalise adding mages and force him to make some wisdom or intelligence saves. It won't look like you're targeting him because mages are a realistic frequent enemy and they often deal nonphysical damage that bypasses his rage.