A comment about his children triggered Ryan Knowles into stamping on another man’s head at a flat in Dunfermline.
Knowles placed Stuart Duncan into the recovery position after subjecting him to the attack on October 19.
At Dunfermline Sheriff Court, fiscal depute Joanne Smith explained the two had been drinking with others at a friend’s flat.
Ms Smith said: “An argument started which seems to have arisen from a comment which had been made about the accused’s children.
“It seems the red mist came down.”
Knowles, 28, repeatedly punched Mr Duncan’s face and knee’d him to the ground.
Ms Smith said: “The accused kicked him to the back of the head three or four times and stamped on his head also.
“It appeared to one of the witnesses that the complainer was now unconscious.
“Witnesses present wanted to intervene but were too afraid.
“One of the witnesses left the room to call police.”
Knowles had fled the scene by the time they arrived.
Police found Mr Duncan with lacerations to his cheek and chin and severe swelling around his eye socket and cheekbone.
The 30-year-old was taken to hospital, where he received stitches.
Knowles, of HMP Edinburgh, admitted assaulting and severely injuring Mr Duncan.
Defence counsel William Adam said: “He’s very much a different person from the person who committed these offences.
“He was a heavy drug user.
“He did put him in the recovery position and left.
“He’s got himself clean and clear of drugs.
Knowles also admitted acting in an abusive manner towards police who were moving him while he was in custody on November 3.
He shouted, swore and repeatedly uttered derogatory remarks towards officers, as well as spitting on one.
Sheriff Keith O’Mahony deferred sentence for reports.
He said: “I want you to be clear, that’s a serious matter.
“What’s at the forefront of my mind is custody.”
Knowles will be sentenced at Falkirk Sheriff Court on October 18.