You do not need a special scope to kill them. Buy the Killer 7 Magnum and use it on them. After three or four shots, they will go down. Shoot it in the sheet until there is a hole. Then, shoot its head. After that, the body will explode then the legs will fall over and leave 5,000 gold. Additionally, another way to kill the Regenerator creatures is to shoot their head or chest with the shotgun. Then, blast a leg away; it will fall on the ground. Then, take out an incinerator grenade (the red ones) and throw it at them. If done correctly, he will burn on the ground and die.