Willow Rosenberg
Willow Rosenberg is a fictional character from the TV series Buffy the Vampire Slayer. She was played by Alyson Hannigan, and made a couple of special appearances on the Buffy spin-off Angel.
Willow was a meek, nerdy, studious teenage girl who had more success academically than socially, until she became friends with Buffy Summers and started fighting evil alongside her, proving to be courageous and resourceful. At first, her most significant talent in the fight against evil were her computer skills, but progressively Willow gained power as a witch through her study of magic, until she became arguably the most powerful member of the Scooby Gang.
Although the series initially portrayed Willow as a straight character, who had an unrequited crush on her childhood friend Xander Harris, a then a relationship with a boyfriend, Oz, she was rewritten as a self-identified lesbian once they established her character's relationship with Tara Maclay. In the last season of the show, Willow acquired a new girlfriend named Kennedy.
When Tara was murdered by one of Buffy's enemies, Willow used dark magic to avenge her death, and nearly destroyed the world out of grief and rage in the process.