im gonna say shotgunners because there so many of them and they are hitscanners.   chaingunners are even worse but im not afraid of them that much because there not many of them in doom 2.   zombiemens are meh.   pain elementals sometimes can be very annoying of spawning lost souls but you can kill them relatively fast.   arch-viles not many of them in doom 2 so its alright i guess   revenants are not that scary. homing missiles can be tricky a l