Fiction

though critics debate whether his vigilante justice sometimes crosses the line into villainy
. Reacher does not kill for no reason germane to the storyline; rather, his actions are motivated by his sense of a black-and-white moral code.
Reasons and justification for Reacher's kills:

Vigilante justice: Reacher acts as an instant judge, jury, and executioner for individuals he perceives as deserving of punishment. He has no legal authority to do so, but he is driven by his personal code of right and wrong.
To protect the innocent: A central aspect of Reacher's moral code is the protection of the defenseless and the elimination of those who prey on them. His decision to kill is often tied to ensuring the safety of an innocent person.
To eliminate a threat: For Reacher, a person who cannot be reasoned with or trusted is a danger that must be completely eliminated. His choice to kill can be a matter of his own survival or the safety of others.
Revenge: In some cases, Reacher's actions are driven by revenge. For example, in Season 2 of the TV series, he goes on a killing spree to exact revenge on the people who murdered his brother and his former army colleagues.

Criticisms of Reacher's kills:

Excessive violence: On occasion, Reacher's actions are viewed as excessive and unnecessary. A scene in the TV show where he murders a helpless, bedridden suspect by injecting an air embolism provoked criticism from viewers who felt the action made Reacher seem more like a villain than a hero.
Justification vs. murder: Reacher's acts of vigilante justice are interpreted by some as cold-blooded murder, even if the victim was a bad person. Critics argue that killing an unarmed person, regardless of their past actions, is an evil act.
Blurring the line of a hero: While many fans accept Reacher's brutal approach as part of his character, others question if a protagonist committing such extreme acts can still be considered heroic.