Dr. Killebrew is the doctor who treated Deadpool at the Weapon X program. Wade has an intense hatred for the man, even after Killebrew was trying to atone for his deeds and even helped rescue Wade when he was sick. It was the mutant Siryn who convinced Wade not to kill Killebrew.
Killebrew and Deadpool met in the following comics:
Deadpool (volume 1) #3
Deadpool (volume 3) #11 (fantasy)