It depends on the brake, rear brake at speed will only cause it to fishtail, maybe skid a bit, can be epic. Grabbing the front is triggering the trebuchet, a different kind of epic.
In the comic above the right hand is typically the front on motorcycles and bikes. (Some bikes in Europe reverse the layout and have the right brake as the rear, though.)
It depends on the brake, rear brake at speed will only cause it to fishtail, maybe skid a bit, can be epic. Grabbing the front is triggering the trebuchet, a different kind of epic.
In the comic above the right hand is typically the front on motorcycles and bikes. (Some bikes in Europe reverse the layout and have the right brake as the rear, though.)