A teenager who punched an off-duty prison officer, causing permanent brain damage, has been found guilty of intentional grievous bodily harm.
Jamie Nethercot skipped and jumped about after delivering the forceful blow, Leicester Crown Court heard.
The 19-year-old accepted he caused devastating injuries, but said he did not intend serious harm.
The 34-year-old victim, a married father, was on a night out.
He fell backwards, hitting his head hard on a kerb or step.
He had life-saving surgery, which involved having part of his skull and brain removed.
He was left with "severe and life-changing injuries," said Rebecca Herbert, prosecuting.
Nethercot, of Pollard Road, Braunstone, Leicester, admitted grievous bodily harm (GBH), but denied GBH with intent.
A jury of nine women and three men convicted him unanimously of the more serious charge.
Nethercot also admitted causing an affray during an earlier assault on the same victim that night – July 21 last year.
Nethercot was remanded into custody for sentencing on May 3.
Mrs Herbert said Nethercot first targeted the victim, who was unknown to him, with an unprovoked head-butt on the dance floor of the Lamplighter's pub, on the corner of Silver Street and High Street.
When he saw the victim outside moments later, he crossed the road and floored him.
Mrs Herbert said: "What happened to the victim is something that may send a chill through all of you.
"It's the type of thing, due to the activities of men like the defendant, that could happen to anyone who was in the city centre on a night out."