Leela (played by Louise Jameson) was a purple-haired chick from the year 3000 with one eye a companion to the Fourth Doctor from 1977-1978. Famed for her skimpy costume and tendency to kill every motherfucker in the room, she eventually left the Doctor to live on Gallifrey. Presumably now dead of Time War.
Leela was a member of the Sevateem Tribe until she was exiled for heresy (and killing everyone with Janis thorns.)
Leela's murderous nature made her an extra-based companion (much like Ace and Captain Jack in later years) because this allowed the Doctor to retain the moral high ground and not get his hands dirty while she got down to business slitting motherfucker's throats.