You know what's interesting about these two guys? If you take them separately, not much. But together they bookend the way the novel shows the army experience. Or, more accurately, the officer experience (since we don't get more than just a few anonymous looks at how the cannon fodder troops roll).
On the one hand, you've got Denisov, who is an all-around swell guy, a safe early boyfriend for Natasha, and an officer who generously shows Nikolai the ropes and grooms him to eventually become a good officer in his own right.
On the other hand, Dolokhov. What can we say about Dolokhov? He's basically kind of a psychopath (seriously – we meet him right when he decides to tie a policeman back to back with a bear and then throw them like that into a river – that's some Law & Order: SVU insanity, right there). But the army is probably the best place for him – he gets to kill a lot of people and it actually plays pretty well.
Why do you think Tolstoy put Denisov and Dolokhov together on that guerilla warfare team at the end of the book? Does seeing them side by side change how we feel about either of them? How do we react to what they are or aren't willing to do? Does Dolokhov's heroism mitigate his misdeeds?