Like most superheroes, Guy abhors killing and usually avoids it at all costs. He has provided a number of reasons for this. While he adheres to a strict moral code, he is not entirely inflexible when the situation he finds himself in calls for him to take actions towards the greater good.

During his time with the Corpse, although leader Von Daggle required him to assassinate targets, he had an inner struggle, and ultimately could not bring himself to perform an execution like that. He later explained that killing someone is the "easy" way out, and his style is making the scum of the universe face the music. At the climax of the Sinestro Corps War, when usage of lethal force was enabled for regular Corps members, he was faced with this dilemma again. Trapped and cornered, he had no option but to kill the Sinestros around him in self-defense. Although he expressed reluctance, and concern about keeping up with the standards of his friends, he was willing to if he had to. The choice was taken out of his hands by a wave of Lanterns who came crashing down onto his position and saved him the trouble. He very strongly opposed the executions carried out by the Alpha Lantern Corps during Emerald Eclipse. Sciencell prisoners who participated in the riots were rounded up and killed by mandate of the Guardians. Guy was irate that they were sacrificing the ideals of the Corps by killing unarmed people in cold blood and without trials. Unfortunately, though he argued himself into a suspension, he was unable to prevent the slaughter. However, Guy has killed before in the line of duty. Duel Eknham met his fate at Guy's ring after attempting to kill him and his friends, although the villain had already been divided in half by Mongul.

However, he has at times taken an active immoral stance in his tenure as a superhero such as during his time as the "Warrior" where he decided he would be the bad guy or "garbage man" that would take care of the messes and dirty business that more straight-laced heroes strayed away from. As such he developed a poor reputation among the superhero community and is often seen as an abrasive thug by his peers.

He also has a personal code of honor about fighting. While teaming up with Lobo, who was brutalizing Qwardians, the two had a discrepancy about their personal approaches to violence. Guy had enjoyed kicking their butts, but disapproved of torturing them needlessly afterward, because there was no challenge in beating guys who were already beaten, and no point. Lobo accused him of having a soft spot, which he resented. He also took personal fault with the nuclear arms race early in his career, because there was no glory in missile warfare, and he believed combat should be man-to-man.

• Green Lantern
  • Green Lantern