"Sickening" CCTV images have been released showing a man repeatedly stamping on a teenager's head as he lay unconscious on the floor.
The 18-year-old was knocked over by a man in Birmingham, before being punched to the ground when he challenged him and stamped on up to 10 times.
It was feared the victim may lose the sight in one eye, following the attack in Broad Street, near the city centre.
The full CCTV footage is too shocking to release, West Midlands Police said.
Detectives hope the images will help trace the victim's attacker, who struck at about 04:00 BST on 9 September.
The victim's sight has since returned, but police said he suffered serious facial injuries and lost several teeth in the incident.
Det Con Sarah McDonnell said: "The victim was a totally innocent party.
"He got caught up in an incident and was understandably unhappy at being shoved to the ground.
"He approached the aggressor and was then punched to the floor and repeatedly stamped upon.
"He was lying prone, face down on the floor, and unable to defend himself it is the most cowardly, sickening attack I've ever seen and I'd urge anyone who recognises the offender or any of his friends shown on CCTV to contact us.
"The attacker, who was having an altercation with another group moments earlier, is seen on camera seemingly trying to justify his actions to some of the throng of people who gathered at the scene before he nonchalantly slopes off.
"Many people witnessed the attack and I'd also ask them to come forward and report what they saw; they could hold important information."