I have killed him 2 times (playing the campaign the second time now), both times I succeeded by first using the Ion cannon then the redhand autolaser (one lasergun clip got him down after 4-5 Ion cannon rounds).

Good luck, just make sure you turn around and give him a rocket, Ion cannon round or anything else very powerful, and he will back up and give you a chance to finish him off. Do not waste rifle ammo, only the laser, Ion cannon or rocket launcher, because you will have to fight tons of enemies later with what you´ve got, then you´ll need the ammo until you find more.

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