Disclaimer: don't own Young Justice because (insert clever reasoning here)
Many times they come back quiet and afraid. If someone's hurt they're immediately taken to a medical facility, if they haven't already. The rest of the team climbs out of the Bioship wearily and goes straight to them rooms, reconvening only a few minutes later. Maskless and in civvies, they quickly transport to wherever their injured teammate is. And they remain there for however long it takes to see them, whether awake or unconscious (like the time Artemis had her arm brutally snapped by some thug or when Aqualad laid in the desert so long he almost died). But eventually their mentors wake them and bring the heroes home, sometimes complaining but usually too tired to speak. It's an unspoken rule that you come visit whenever you can. And eventually they're a team again (alwaysalways always)
Rarely do they come back silent and stunned. If someone's died, but it villain, victim or hero, they try to bring the body back while trying to look anywhere but the corpse. No one cries on the way back to Mr. Justice, still trying to grasp what happened. They drift apart immediately once they land, ignoring their chaperones' worried gazes in favor of showers and alone time. But the need to have comfort in an hour so dark soon overrides pride and one by one, they gather in someone's bedroom: usually the one who's witnessed it, or whoever's been most affected for whatever reason (like the time Miss Martian accidently broke a murderer's mind or when Superboy fell on an innocent passerby). They hold each other, cry at least a little, but they don't talk—they know words can't do anything just yet. No one leaves until they all do, because they're family and families never leave each other no matter what (stay stay stay)
But mostly, they come back triumphant and gleeful. If someone's bleeding or bruised, they're patched up quickly, but usually the worst injury is a broken bone or concussion. Debriefing is the only serious part of the night—or day—but even Batman drops a few words of congratulations. Later they shower and change, the adrenalin still running in their systems, before changing into the kitchen. Sometimes Black Canary or one of their mentors drops off Chinese or pizza or burgers, or they'll just dig around in the impossibly large fridge. Maybe they'll start a movie or video games, but usually they spend the night talking and laughing and flirting and remembering (like the time Robin walked in on Wally and Artemis making out or Connor's reaction to Kaldur's very patient Talk—you know, The Talk—or when Megan finally perfected her cookie recipie). Eventually they crash on the couch, cuddling and drooling and snoring and together (forever forever forever)
A/N: I'm going on the assumption that they all crash at Mt. Justice after a mission, because let's admit it, no one wants to be alone when the adrenalin's still in ya. I think. I don't, at least ^.^
Also, on the killing thing-they're kids, really, and Megan and Superboy especially, they all lack experience. They make mistakes. The thing that makes them heroes is that they keep at it and never give up.
If someone can tell me every single pattern I used here (I think there's, like, five or something) I will write you a personalized YJ oneshot-except if I don't like your pairings I won't but whatever.
Review munchlets! My own word ;)