Stop fighting or I will shoot you!
BOSS! Gets in your face but does not fire unless someone else fires in her presence. Then she retaliates with great conviction against whoever fired.
ScorpionBot shoots before a would-be-shooter, so against softer enemies you can just walk into them and let her pick them off before they can hurt you. If the target survives, you will be hurt; on higher difficulties enemy bots can deal so much damage that letting them shoot you in order to provoke the ScorpionBot into shooting them becomes impractical.
Damaging her without attracting return fire can be difficult; one way is to lure her into mines or Sentry Turrets. If she's hugging you while you need some space to work with, go into stealth for a few turns.