Dylan Whittingslow, 19, pleaded guilty to one charge in a County Court sitting in Ballarat of recklessly cause serious injury, which left the victim in an induced coma for three days.

The court heard on March 30, 2013, Whittingslow and a friend bumped into the victim and another male.

Judge Paul Grant said the pair had "bad blood" and Whittingslow had previously threatened the victim.

The court heard Whittingslow went to shake the victim's hand and punched him in the chin, causing the victim to fall back and hit his head on the floor.

Whittinsglow stood over the victim and said "I've been searching for you for many years and now I've finally found you".

Judge Grant said the victim heard Whittingslow say "I think I've killed him" before leaving the scene.

Summarising the victim impact statement, Judge Grant said the offence had a significant impact on the victim's family, with the mother describing it as a "parent's worst nightmare".

The statement went on to say the victim had suffered a dramatic change of character since the accident.

Judge Grant said: "This is just another case of a young man in an unprovoked way punching someone in the face and giving them life threatening injuries."

He said Whittingslow, who had priors for being drunk, assaulting police and resisting arrest, was charged with resisting arrest and affray just three weeks after being bailed for punching the victim.

However, Judge Grant said he was satisfied with the victim's remorse and prospects for rehabilitation, provided he stayed clear of his problems with alcohol.

"You're still a young man at 19, and you were 18 at the time of the offence, however the seriousness of the offence means appropriate weight must be given to the principles of deterrence."

Judge Grant said if Whittingslow, who registered an early guilt plea, had been found guilty by trial he would have received three years and three months in prison.

The maximum prison sentence for recklessly causing serious injury is 15 years.