Poison Kiss was a member of the Mad Gear Gang that terrorized the streets of Metro City until they were defeated by Mike Haggar, Guy, and Cody. When Sodom brought back together the gang, she was once again recruited but they were defeated by Metro City's heroes without a sweat. In a life with no more prospects, she decided to end her criminal life and helped her friend Hugo in his wrestler career becoming his manager. Finally life was smiling to them and with Poison's help, Hugo became a huge star in the wrestling circuit, becaming both of the rich and famous.
Poison's life is full of controversy. In the official story of the Japanese version of Final Fight, Poison is a pre-operation transsexual.
Taking into consideration that hitting a girl in a videogame was pretty inadecuate. Both Poison and Roxy (the cloned version) were eliminated from the American version of game and replaced with Sid and Billy, making things more tolerable for Nintendo but not for Poison.