[boogiewoogie]

If the umpire thinks it's intentional then the pitcher will be ejected. Or if only the batter thinks it was intentional then you might have a brawl https://youtu.be/4APOqlpyseM

[blackbagboys]

A recent example of this is Bryce Harper being nailed by Hunter Strickland and taking it personally: https://www.youtube.com/watch?v=0w6tEO81kAY