Drusilla

Drusilla was sired by Angelus, who first made her insane by killing all the people she loved.
Dru sired William, an English gentleman who became known as Spike when he was turned.
Drusilla left Spike in 1998 for a Chos Demon. She killed her first slayer Kendra, in Sunnydale.
Dru returned to Sunnydale later on to try to get Spike back,
so herself, Darla, Spike and Angel would be a happy family again.
Drusilla went to LA to revamp the now human Darla, which she did and Darla & Dru went on a shopping spree, well more like a massacre untill they were stopped by Angel and Wolfraham & Hart.