Mother Brain
Mother Brain is the leader of the evil Space Pirates in the Metroid series of video games. She usually appears as the final boss. Not the most intimidating of villains, she's in essence a huge one-eyed brain in a jar. Her attacks consist of the automated defense systems surrounding her, though the eye may join in once the jar is ruptured.
In her appearance as a supervillain in Captain N, she had gained a snooty female "face". Whether or not putting a face on a brain is an improvement is debatable.
Games
Mother Brain is defeated by first breaking her tank with missiles, and then pummeling the brain itself. In Super Metroid, she has an ace up her sleeve: after the destruction of Mother Brain's tank, she grows significantly and must be defeated in her new, larger form.
She is notorious for her use of a villain cliché: Her seeming death initiates a self-destruct device, giving the player only a few minutes to escape before the area/atmosphere/planet is incinerated.
