Mark Grayson the eponymous hero of Invincible is the eptoime of this. At first he was typical The Cape who beleived in Thou Shall Not Kill but after several instances where he's loved ones such as his mother, girlfriend/future wife Eve and little brother were place in mortal peril, Mark decided he shoudn't be merciful againist villains who would happily kill the innocent. His brutal fight with Conquest in particular, cumilnated in him headbutting Conquest face into a bloody pulp after the latter had almost killed Eve. Mark is a good man, but anyone who harms his friends and family will fucking pay for it, as the abusive boyfriend who hurt his ex Amber learned the hard way with Mark dangling him off a building and warning him to never touch or go near Amber again.
Miyamoto Usagi from Usagi Yojimbo is kind, courteous, and soft-spoken, and he will try to talk his way out of bad situations before they turn violent. That is a principle of bushido, albeit one that isn't very widely observed in the world Usagi inhabits. But those who oppress the weak or try to harm Usagi's friends or family will discover that he's just as diligent about following the martial code of bushido as well. A regular deliverer of the Curb-Stomp Battle or even Single-Stroke Battle.
In Empowered the Maidman (one of Empowered's very few friends) is one of the few nice-guy vigilantes in a field dominated by douchecapes, but he says, "I find that severe physical and emotional trauma works wonders for disincentivizing even the most dedicated miscreants.... If necessary, career-ending injuries are a helpful tool for dissuading continued supercriminality."
My Little Pony is a prime example of this. No, really! In the original series comics, the ponies' leader Majesty had the power of transmutation, and though she didn't do it to everyone who displeased her, there were several occasions on which the enemy's punishment was being Taken for Granite. Some were left in And I Must Scream condition. (Chalk that up to the writers being hesitant to have an enemy killed outright... most readers agreed, though, that showing the villains as still sentient and cursing their defeat doesn't count as softening their sentence when they've been left in the form of bubbles that will endlessly float around the moat of their castle.)
Paperinik, as expected from the superhero identity of Donald Duck. With his friends and family he's nice and polite, even if easily angered. With his enemies? Well, the Evronians are emotionally crippled, and one that had a tour of duty on Earth is shown to be horribly traumatized by the beatings Paperinik gave him.
This comes straight from the "classic" Paperinik stories, where Paperinik has developed a Friendly Enemies relationship with most of Duckburg's criminals because they know they can't beat or escape him but if they give up without trying either they'll at least dodge the beating. That was learned with such lessons as Paperinik setting a lynching mob on the Beagle Boys for falsely claiming they knew his identity.
Lyla Lay is one of the friendliest characters in the cast. She's also a droid agent of the Time Police, who, when required by her duties, has gone into combat by shooting to kill.
Urk is a polite man, who, upon being stranded in Paperinik's dimension, took the time and effort to learn the language and customs of this new place and take a normal job, while also making sure to help anyone in need when he could. He's also an Iroquois warrior, chosen as the future leader of his people for his bravery and success in battle against the Viking invaders, and got stranded in Paperinik's world while chasing a time-eating monster with intent to kill it if he can or contain it if he can't.
Angel & Faith: Faith's compassion has reached the point to where The Dead Have Names and Even Evil Has Loved Ones in regards to vampire drug dealers, while slicing off the arms of human gangsters who threaten her and Angel and attempting to forcibly turn him human so he can let go of having to make amends.
Star Trek (IDW): Sulu is prone to many badass moments throughout the series, which prompts Section 31 to attempt to recruit him into their ranks. When that fails, they recruit his sister instead.
