Like the minigun? When mounted, instant death to anything in the general direction that it's pointed in.
While I often complain about the new grenade pistol, I do have to be reasonable and point out a few things. I set weapon damage back to the defaults, so the grenade is only an instant kill when it actually hits someone. If it explodes near them, only death if they had been previously wounded. Same with the submachinegun's dart, which is usually followed up with a burst resulting in a headshot anyways.
The peacemaker is just OP. No excuses for that weapon, ever. Dark Star, at least it isn't hitscan so it takes practice and luck to hit anything at range.