Sun Woman was a one off villainess in the Legion of Super-Heroes.
Seeking admission to the Legion, Night Girl is given the challenge of capturing Sun Woman, who had set herself up as a tyrant on the planet Vannar, half of which was in perpetual daylight. Sun Woman had stolen a solar energy harness that captured solar power and gave her invincible strength. She used her strength to tear down the houses of people on Vannar, so she could enlarge her palace.
Sun Woman dismissed Night Girl as a 'snip of a weak girl,' and had her thrown in the dungeons. She had not realized that the darkness of the dungeons would maximize Night Girl's strength. Night Girl tunneled out of the dungeon. She then commanded the people of Vannar to light bonfires. The smoke blocked out the solar energy, taking away Sun Woman's strength. Night Girl then announced that she would be taking Sun Woman to face justice.
We last see Sun Woman in chains, being flown into space by Night Girl. She looks incredibly annoyed. As she makes no return appearance, she probably got a very long sentence on the prison planet of Takron-Galtos.
Sun Woman is bound and taken away to prison.
Fan art by Inspector97