Volatile mod. It increases the draw time. The only bows capable of one shot are high impact bows which go from about 767 to about 1500. In return it gives about a 100% damage buff + an explosion. Volatile mods are overpowered in general like the shotgun one that increased the rpm of shotguns all the way up to 900 rpm and allowed them to fire every shot without reloading. They're only active as well in Arms Week specific pvp. You're specifically going into a match where these mods are allowed.