Luke Andrew Rusher, 27, of Penna, pleaded guilty last week to causing grievous bodily harm in November 2012.

The assault, which could have killed the man, happened in the Pembroke Hotel, where Rusher had twice before been convicted over violence.

The court heard that Rusher walked up the victim, who he believed had bullied him more than 10 years ago, and punched him in the back of the head.

The man collapsed and hit his head on the cement outside the pub.

Medical examinations revealed a fracture to the base of his skull.

A a result of the attack, he suffers profound hearing loss in his right ear.

The court heard that the victim had no involvement in the old bullying incident that apparently upset Rusher on the night.

"To strike someone in such a cowardly way is completely unjustifiable and unacceptable," Justice David Porter said in the Hobart Supreme Court this week.

"Your conduct was fraught with danger and might well have resulted in death."

He said Rusher had been given a six-month jail sentence in 2010, suspended for three years, for an assault in the same pub.

Justice Porter ordered that he now serve that sentence and added another 21 months' jail for the 2012 assault.

Rusher will be eligible for parole in August 2015.