I just made a post about this on the Galaxy Cauldron Forums so I decided to post it here as well!
I feel like Galaxia redeemed herself through death.. Unlike in the anime, where Galaxia was under the control of Chaos and had no control of her actions, Manga!Galaxia was fully aware of what she was doing; she wanted to become GOD, and to do so, had to wipe out all existing creation. Yes, it’s true that she had been manipulated by Chaos, but not outright controlled; she still very much had free will and was well aware of her actions and their consequences.
Anime!Galaxia was able to redeem herself by returning the stolen star seeds; in the manga, it seems like it’s not so clear-cut and simple. Instead of people immediately popping out of their star seeds, it seems like they actually need to CULTIVATE again and grow back on their own accord. So Galaxia wouldn’t be able to redeem herself that way.
Let’s put this in an earthly perspective; You’re sitting at home, just relaxing and watching tv, when a documentary about a serial killer who killed over 15 people comes on. You’re interested so you sit in and listen. The documentary mentions that said killer had an abusive childhood and brutalized from a young age. While this certainly may explain WHY this individual killed (and this is where the whole nature vs. nurture argument comes in), does it give them an EXCUSE? Does being abused give you an excuse to be the abuser?
NO. No matter how unfortunate your past may have been, that doesn’t give you an excuse to act out on your rage. We never really understand WHAT made Galaxia’s past so horrible, although it seems very likely that she wasn’t really abused… In fact, I don’t think she had any people in her life whatsoever. I think she was all alone on that “trash” planet. She became so power hungry because she confused that empty feeling inside of her for a lust for power instead of a longing for love. Due to the lack of people in her life, she was unable to develop empathy or form bonds of any kind. She was able to slaughter millions because she couldn’t form any kind of empathetic connection to anyone. Does this give her an excuse? Like with the serial killer above, certainly not, but it may help to EXPLAIN.
This is getting kind of long winded, haha, but although I adore Galaxia and she’s my fave villain alongside M9, I’m happy Takeuchi killed her off the way she did. Galaxia was finally able to understand why she felt so empty; she had never experienced love, to love or be loved. After witnessing and experiencing Sailor Moon’s all encompassing love, she was finally able to get a glimpse of what she had missed and was remorseful. She didn’t fight death because she knew it was what she deserved.