Love the fact that the killcode seems to be so easily influenced by kindness, more often than not
KC was evil. Then Glamrock Freddy was nice to him, and he started changing
Eclipse was evil, then Earth started being nice to him, and he changed, too
Solar, who'd also be partially made from his Moon's killcode, could've been feral and an absolute menace, but his Sun showed him kindness and acceptance, and he mellowed out
TEAPS Moon's killcode only spikes when he gets mad or someone mistreats him and Sun. If people are nice to both of them though, he's completely fine
The only person who had at least a portion of the killcode in them and stayed evil was probably Bloodmoon. Bloodmoon had multiple chances to change, but he chose not to, even after Sun tried to extend the figurative olive branch
We don't know what the story behind FFNAF Eclipse/Clipsie is yet, so I can't say anything regarding her, aside from that whatever happened post accidental creation/awakening, led to her considering Sunny and Moonie as her sisters
Nexus,,, I can't speak for him either, since he doesn't have a killcode. When Moon and KC split, KC physically left and went into another body, left no traces of himself or his code behind
I think Ruin mentioned having a killcode at one point, but I'm not sure. I'd have to do a bunch of digging to find out, but that'd take an ungodly long time
So apparently, if you wanna tame befriend someone who has a killcode in them, the best way to do that would simply be repeated, prolonged exposure to people who will be kind and patient with them
