engineering biological supersoldiers who fight without pain or fear.

Not that hard to do reallyl I don't experience fear or pain in those circumstances, I merely get confused when parts of me get damaged and stop working correctly.  And there are a lot of people out there who have this same trait, inserting that gene pattern into a genetic mix that includes mindless loyalty and obedience can be a very scary thing.  Particularly mixed with extreme athletic ability and a complete lack of empathy.  Of course you'd have to make them sterile cuz mother nature would definitely fuck-up your programming given half a chance.

Pretty scary shit.