Matthew King, 22, pleaded guilty to assault causing bodily harm, impaired driving, leaving the scene of an accident to escape and two breaches of probation, the Canadian Broadcasting Corp reported.
Court heard from witnesses King drank 24 bottles of beer in August and went out "looking for a fight," VOCM Radio reported.
An unidentified 16-year-old boy whom witnesses said was "in the wrong place at the wrong time" was beaten and kicked into a coma and spent two weeks in hospital, the CBC said.
The victim's mother said as a result of skull and cheekbone fractures, her son has lost his sense of smell, suffers from peripheral vision loss, and has no conception of time, VOCM said.
At King's sentencing, he broke into a rap song he wrote that included such lines as "The Bible says God forgives us our sins ... May him strike me dead next time I wanna throw a fist."
He will be sentenced Tuesday with prosecutors requesting he receive at least a 2-year prison term, the reports said.