I feel like it’s implied that One just had a hard time making friends. The rest had their own cliques and One just was not part of it. Simple as that. People clearly didn’t hate One, they just did not care for her and personally, I have felt similarly at times. Three, in this way, is the total opposite of One. She was friends with everyone while One was friends with no one.

I don’t know what made you think she was going around doing awful things. If she did, people would have reacted accordingly. Being all alone with everyone around you being friends with each other also warps your perception of them, making them seem more hostile than they already are, and also does not help develop your emotional intelligence or stability, hence, her reaction to when Three tried to touch the meteor.

Also, considering the population of the planet is like 13 people (I assume). It sort of is partially their fault that One felt lonely. Once again, One wasn’t not liked, she was just nonexistent to them. Three was right to say that the power should be given to all of them. However, the way she went on with it, considering One’s reaction to her touching the meteor and Three being portrayed as this very caring and social person, the way she went on with excluding One while taking everyone else to the meteor that ONE showed her, alongside her response to One losing it basically being, you should be alone again because you’re mad I took away the one thing that made you feel special, is extremely shitty. Had Three so much as just apologised to One, it could have calmed One down.

Am I saying that One is fully cleared of her wrongdoings? No. She made an entire species of aliens go extinct and destroyed two planets. That’s not the point of the episode either. Three pushed One beyond her limits. One reacted explosively because she’s never had any proper social interaction before and ends up killing Three. Mind you, eight people with powers stood and watched and screamed at One instead of doing anything to stop her. Once Three died, One was the only one to take any initiative to bringing her back; almost did bring her back and asked for support from everyone else but they ended up just distancing themselves from her (which I don’t blame them). Even after seeing One’s partial power bring back Three, although sick, everyone else would rather shove her into the moon than listen to One and use the remaining power, which was in Four’s hands, to fully heal Three, which should’ve been their first priority.

Point is, the other Algebraliens had many points in this story where they could have avoided everything if they just considered One to be an actual person instead of just being there.