Chantho

Chantho was a female Malmooth, and presumably the last of her kind.

Biography
Chantho left the Malmooth Conglomeration and worked with Professor Yana of the Utopia Project. Chantho felt an unrequited love for Yana. She confessed this to Martha Jones, who sympathised with her, having similar feelings for the Tenth Doctor. When Yana discovered that he was in fact the Master in human form, he fatally wounded Chantho with a live electric cable. With her dying breath, she shot the Master, triggering his regeneration. (DW: Utopia)

Personality
To be polite, Chantho, like all Malmooth, had to say the start of his/her name at the beginning of each sentence, then finish with its end. When Martha asked what would happen if she didn't speak that way, her reply was, "Chan-That would be rude-tho.", like swearing to humans. However, she was able to overcome this with a certain degree of effort, as she demonstrated to Martha saying "...No.", which Martha found amusing. (DW: Utopia)

When Davros asked the Tenth Doctor "How many have died in your name?", the Doctor recalled Chantho's death. (DW: Journey's End)