Because you know, he stole the silmarilions and destroyed the trees? what comparison
And where exactly state she defeat Sauron, and alone at that? i know she and Beren took one of the silmarilions from morgoth crown, but nothing about she defeating sauron.Luthien was still an elf, regardless of her lineage, and took on Sauron. Just as an elf took on Melkor/Morgoth. It seems Tolkien made sure his elves had no issue with fighting above their level.
You have to understand that there is no 'regardless of lineage" if they were born directly from the maiar, basically lesser gods of the setting, they are basically demigods without their blood being diminished, far superior to other elves, is like comparing humans with the blood of numenor to normal humans.