The Ecolitan Operation by L.E. Modesitt Jr
Major Jimjoy Wright is the Empire’s most successful secret agent. That’s because he’s strong, brave, clever, deceptive, ruthless, and totally goal-oriented. Once he accepts a mission from his government, nothing gets in his way. He always gets the job done.
Though JimJoy thinks he’s highly ethical, most people would find his consequentialism to be psychopathic. For example, JimJoy is responsible for the deaths of tens of thousands of innocent people. This doesn’t bother him because if he hadn’t destroyed them, millions of other innocent people probably would have died (it’s like an extreme version of the Trolley Problem).