Well. This has taken a fascinating turn. We're at the girls-pulling-swords-out-of-lakes phase of the story.
Giganta (real name Doris Zuel), is a size-shifting supervillain from DC Comics. She was a scientist who attempted to cure herself of a fatal blood disease, and later became a frequent enemy of Wonder Woman as well as the Justice League.
Originally little more than an ape she was artificially evolved by Gorilla Grodd into a human female (both in appearance and mannerism): she in turn became very devoted to him and also gained the ability to grow to gigantic heights at will.
This served to make Giganta a formidable opponent to any hero in the DC universe and although she began her career as somewhat of a savage complete with leopard-skin clothing she would evolve into a much more refined woman, albeit still a dangerous criminal, as the series and comics went on.
It is worth noting that there are many variations of Giganta depending on the era or writer and her origin varied greatly as do her powers depending on who writes her - though modern writers tend to stick with the size-shifting hyper-evolved ape (this is also the version that was made popular in the cartoon series Justice League).
Another popular version of Giganta was in Superfriends, where she was shown as the rival to Apache Chief, and was present as his superheroic debut. She had been an ordinary woman horseback riding when she saw the effect of the magic powder and desired to use it to become famous.
She stole the bag of powder from Apache Chief when he was busy. Although warned by Apache Chief's sachem to leave it alone as the effects multiply emotions, she ignored the warning. True to form, her selfishness was multiplied along with her size, and she became an evil giantess.
Powers & Abilities
Size Alteration: Giganta can increase her size.
Superhuman Strength: As she increases her size, the stronger she becomes. At her peak, she is portrayed as stronger than Wonder Woman.
Superhuman Durability: As she increases her size, she gains super durability.
Sonic Cry: Once she is gigantic, Zuel's voice can use her voice to shout or scream, damaging or stunning her opponents.
Genius-level Intellect: Zuel was a brilliant scientist.