Hua Tuo
Cao Cao's biography in the "Sanguozhi" mentions that he died in Luoyang in 220 at the age of 66 (by East Asian age reckoning). Hua Tuo's biography mentions that Cao Cao had Hua Tuo executed when Hua Tuo refused to treat his chronic headaches. Cao Cao regretted killing Hua Tuo because his son Cao Chong died from illness, and he believed that Hua Tuo could have cured Cao Chong. Hua Tuo's biography does not specify his year of death, but it is certain that he died before 208, the year in which Cao Chong died. Therefore, the story in "Sanguo Yanyi" is entirely fictional.