Ewan Dow, 25, attacked Daniel Turner, 21, with "determined brutality" in Riverside Park in Glenrothes, Fife, on October 18 last year.
Both lived in the town and were known to each other, but were not friends.
Dow had previously pled guilty to the murder.
Sentencing him at the High Court in Glasgow, Lord Turnbull said he must serve 18-and-a-half years before he is eligible for parole.
The judge said there was no justification for Dow's attack on Mr Turner.
He said: "You had simply decided you would vent your frustration and anger and that he was to serve as the victim for that purpose. He was presumably selected because of his placid manner."
Dow, who had three previous assault convictions, had been binge-drinking for a week and had a "very limited recollection" of what happened.