Instructions
Shoot from as far away as possible without being seen. While you are crouching, on screen indicators let you know whether or not you are hidden. If you score a hit while hidden, you get a damage multiplier for sneak attacks that often kills an enemy instantly, depending on the player's level.
Use explosives, especially mines and frag grenades while approaching the Radscorpion. Insect-type enemies with hard carapaces are usually weak to explosion damage.
Attack with melee weapons while circle-strafing or backing away continuously. This is the fastest way to kill these enemies, but more risky since you will be close enough to be hit by the stinger. A melee-oriented character can kill a Radscorpion in one or two hits.