Self defense assumes a certain level of avoidance or attempts to avoid confrontation (ianal). Marching into a cultists hideout to slaughter demon-worshippers before they kill a virgin to summon a vrock might be justified, but it's still murder and still evil, by that definition. Fighting fire with fire, or evil with evil.
once again you DIDN'T use defense of self or other there... Yes if you just say "Hey I dislike that cult's religion let me go kill them" that is murder.
If on the other hand the cult kidnapped 10 people and you go to rescue them and end up killing half the cult and only rescue 8 of them lossing 2, THAT is defense of other (a rescue mission) and NOT murder.
lets run through my current PC
game 1 hired to protect a caravan... 2 attacks on route 1 I killed people 1 I let them run, but both combat were self defense.
game 2 arravied at town and found out goblins kidnapped some people (maybe working for weird woods witch). Went into wood and met druid/nymph found out that the goblins used to be her desciples but left when a hobgoblin demonologist showed up... with her help we tracked goblins to some caves. He tried to talk to goblins they attacked, we killed 1 and let other 3 flee
game 3 we entered the cave announcing ourselves (my character is a wizard/artificer with a magic box that plays a strong gatar string when I enter places) and tried to make contact with Hobgoblin... we were attacked, almost blew up the mine (didn't know the caves had magic stuff in it that absobs magic and goes boom)
game 4 continued into caves... 2 more combat encounters (we were WAY more careful) found some of the kidnapped towns folk and ran into the hobgoblin who we let monolog... we explained he could let us get the others back and leave or 'do this the hard way' he informed us he already sacrificed to his demon lord... we then heard the demon in our heads 'tempting' us and we made fun of the demon for a bit cause he totally didn't understand what we wanted... game 4 ended with a stalemate us taking the people home we could save
game 5 started with the mayor yelling at us why didn't we kill the demon whorshipers we told him he paid us to return villagers not to be assassins.
game 6 the apothacary in the town turned out to be a necromancer we spent most of game jokeing and fooling around in town until we stumbled on this and a wight attacked us... we killed the wight
game 7 started with the apothecary attacking us to preserve her secret... we DID kill her and take her stuff but she did try to kill us first
game 8 (back to the cave) a big sky laser shot out of the mine/cave with the hobgoblin and we went to investigate... and on way got attacked by bandits... We threw them a +1 spear and some gems and told them to go make money as mercanaries instead.
we got to caves and were attacked by demonic goblins and undead. We killed them not feeling bad at all
game 9 still at cave with sky beam, we fought another group of demon things (careful don't want to blow up mine) then got to the center chamber where a demon prince and hobgoblin were bargoning... We gave demon 1 chance to 'just go home we REALLY don't want to do this' but ended up fighting and killing both hobgoblin and him (to our and it's suprise it was really dying not just going home to abyss)
game 10 back at town everything was weird, and we told them about the magic mineral we forgot tot ell them about before and that they can mine it and be rich. We made friends with captian of the guard and gave her a +1 longsword and breastplate of acid resistance. When we went to bed we all felt sick and even those of us that were elves slept (passed out)
game 11 we woke up the town was deserted run down and now in a drought... we faught some undead.
game 12 still trying to figure things out we headed back to the caves/mines but stopped by dryad... but her tree had long since withered
got to caves and they were a quarry already strip mined (we thought we got jumped to a post apocolptic future at this point)
game 13 we traveled until attacked by a giant, we ended up stopping the fight and making friends... he said the year and it didn't line up with our calander at all, and we made some hard know/lore rolls and realized it was the same year but on older calander date system meant that the old empire never fell 2,000 years ago.
we continued until we found a caravan heading to 'the oasis' and we tagged along.
game 14 was us trying to blend in at this weird town called the oasis and getting over charged for things and trying to avoid 'the prince' until we learned more... also we found out magic was rare and since we all are casters in 1 way or another we were being treated like royalty.
game 15 we got hired to protect an airship (and it wasn't magic... it had no magic on it) and got a ride to another place... one that would have answers (we hopped) at this point we figured out we pulled a sliders and were on another prime material plane
game 16 was a few fights with weird flying enemies attacking the air ship but we got to 'the rock' and found it had a liabrary... game ended with us talking ourselves into the library.
game 17 was 100% a research game
game 18 we set off to find the artificer that taught me... she was mentioned in records and as such we had to cross some badlands...
we have been 2 games in badlands, we suck at finding things, but I think we found the mountain my dwarven mentor in this reality lives (maybe) every fight was things attacked us and we defended ourselves.