JOIN USThe shocking incident occurred when Gary Alcock, 28, was playing a video game and he got annoyed with his girlfriend's daughter Violet who was crying, distracting him.
He hit her so hard that Violet died from internal bleeding at the Royal Oldham Hospital on January 12, the Manchester Crown Court was told today.
Alcock had a history of violence and had attacked the girl repeatedly during the three weeks leading up to her death, Daily Telegraph reported.
The court was told that Violet's mother, Claire Flanagan, failed to report the abuse because she put her own need for a man ahead of protecting her baby.Alcock had moved in with 22-year-old Flanagan just 48 hours after they started dating.
During the weeks leading up to the fatal attack, he punched, slapped and "sadistically" pinched Violet, leaving her with 35 injuries, including multiple bruises, rib fractures and brain damage.
The court heard that her wounds were comparable to injuries suffered in a car crash.
Judge Clement Goldstone while sentencing the pair said: "You, Gary Alcock, subjected her to repeated violence. You caused injuries to her brain, face, arms and legs with a combination of punches, slaps and - bordering on the sadistic - pinches.
"This was the way you chose to cope with a demanding little girl who demanded your attention and interrupted your time-consuming hobby of playing computer games."
He continued: "Violet was sick, she required changing, she required your time and patience.
"You lost control and your temper in the most unimaginable way. You struck her first in the mouth and then inexplicably and with savage force in the stomach."
The judge ruled that Alcock must serve a minimum of 21 years before he can be considered for parole, the report said.
Last month, Flanagan was cleared of murder but convicted of "causing or allowing" Violet's death by ignoring the abuse. She was jailed for five years.