The war has hardened Abdul.  He comes to accept things that to us seem horrible and pointless and wrong, as simply the way things are in wartime.  He captures the men out of desperation, though doesn't treat them horrible.  I think his guilt prevents him from being around them too much but he does not kill them even when he is encouraged.  His emotions lead him, which is something surprising to think about considering his serious and seemingly apathetic character.  His want to kill Ivan, as well as his choice not to are both actions stemmed from feelings (anger/yearning for revenge and then a switch to compassion, maybe empathy).