Pechorin is nothing if not a master manipulator. Manipulating people and situations is what he does best; it's his way of making his life just that little bit more exciting. As to what effect such manipulation will have on other people, Pechorin is completely indifferent. A completely selfish man, he never stops to think of the immense damage he may be doing to other people.
That being the case, when Pechorin rocks up at the sleepy spa town of Pyatigorsk in the “Princess Mary” section of the novel, we know there's going to be trouble. In case there was any doubt, Pechorin helpfully gives us forewarning of how he's going to conduct himself:
I'm delighted. I love enemies, though not in the Christian way. They amuse me, stir my blood. Being always on the alert, catching their every glance, the hidden meaning of every word, guessing their next step, confounding their plans, pretending to be taken in and then with one fell blow wrecking the whole elaborate fabric of their cunning schemes—that's what I call living!
Pechorin is not content with letting other people live their lives as they see fit. He can’t help manipulating them for his own ends, deliberately stirring up conflict and division just for his own amusement. Unsatisfied with the world, Pechorin cannot understand why anyone else would be satisfied, and so he feels entirely justified in shaking people out of what he regards as their smug, self-satisfied complacency.
In the “Princess Mary” section, this involves an attempt to seduce the eponymous character, even though Pechorin has absolutely no desire to marry her whatsoever. His seduction of Mary has tragic consequences, as Mary is the object of Grushnitsky's affections. He and Pechorin engage in a duel over Mary in which Grushnitsky is killed. Once again, Pechorin, the arch-manipulator, has contrived a situation to his own advantage, playing with people’s emotions and now ending someone’s life.