Video games have come a long way from the days of just shooting/hitting things until they die or you run out of levels, with more agency put on you to either abide by a strict set of rules, or try and break them. None are more widespread amongst the heroes of the land than the ancient commandment, "Thou shalt not kill".
It's generally a rule superheroes abide by, including a friendly neighbourhood gymnast and a brooding billionaire vigilante, but it isn't strictly tied to them. Sometimes an undercover cop wavers on that thin blue line, or a well-meaning prince under orders from his father.
Yet, as games have developed from straight forward "scores for kills" to more complex affairs, sometimes the lines blur on what can and can't be done, or what the hero should abide by. Sometimes a character is forced to go against their "one rule", whether through script or the player deciding to push that boundary to see what they can achieve.
Whatever the reason that drives them, it's hard to ignore that some saintly heroes have straight-up killed people.
10. Batman - Batman: Arkham Knight
Batman's one rule is that he doesn't kill people. A steadfast mantra that stops him becoming just as bad as those he captures, it's the reason Joker never aims to kill him, as he brings order the Joker's chaotic nature. As both player character and hero, there are rules in place to strictly stop you from ending someone's life. Sometimes the odd goon will fall over a railing, but that's not intentional.
However, when the Batmobile gets introduced, all that regard for life goes out the window.
Sure, Rocksteady coded it to shock people that get too close, or fire non-lethal rounds to knock people out (with the latter being the same rounds that tear mechs to shreds), but regardless, we've all ploughed right through squads of enemies, and they clearly didn't ALL get out the way.
To suggest The Dark Knight has his mindfulness about him at all times is also absurd, especially when chasing down Firefly on his pyromaniac rampage. How is Batman going to tell the difference being a speed bump and an unconscious body when he's sliding around corners?
"Because he's Batman" doesn't bring people back from the dead.
Questionably sharp Batarangs is one thing, but a fully equipped mobile tank is something else.