A reveller suffered brain injury when he was knocked unconscious in a New Year city centre pub attack.
The man suffered bleeding and swelling to his brain after his head hit the floor of Dr Feelgood's in Sunderland following a punch just after midnight on January 1.
Newcastle Crown Court heard Darin Brooke had thrown the forceful blow after their groups bumped each other at the doorway of the establishment during the celebrations.
Prosecutor Kevin Wardlaw said the victim had apologised about the collision before Brooke lashed out.
Mr Wardlaw said; "Without warning, the defendant stepped forward and punched the complainant, once.
"The complainant fell backwards onto the bar floor, flat on his back.
"As soon as the complainant hit the floor, the defendant ran out of the front door.
"If the complainant was not unconscious before he hit the ground, he certainly was once he was on the floor."
The court heard the victim suffered a fractured skull and spent a week in hospital.
He has since made a good recovery but had his driving licence taken off him due to a seizure and feels his personality has changed.
The victim needed long term medication and said his job was affected by his injury.
Mr Wardlaw added: "He was concerned because the incident could have been considerably worse, with far reaching consequences."
Brooke, 28, of Marshall Street, Fulwell, Sunderland, who has never been in trouble before, admitted causing grievous bodily harm.
Mr Recorder Paul Kirtley said the incident had been "catastrophic" for the victim as well as his attacker.
The judge told Brooke: "At the age of 28, one could have thought you were one of those people who would never come before the courts.
"It is almost beyond comprehension why you did what you did.
"What you have learned, and what the victim has learned, is that one blow can cause a devastating outcome."
Brooke was sentenced to 18 months imprisonment, suspended for two years, with programme requirements, 150 hours unpaid work and £5,000 compensation order.
Tony Hawks, defending, said Brooke is a hard working, respectable man who has never been in any trouble before.
Mr Haws added: "He was not looking for trouble, he was in the process of trying to go home."