Ryan Tipene Hardman committed a "cowardly act" when he assaulted a 15-year-old.

The 28-year-old Masterton man pleaded guilty to a charge of assault with intent to injure when he appeared before Judge Tony Walsh in Masterton District Court and was told by the judge it was a cowardly thing to attack a young person in such a manner.

The court heard Hardman had gone to the teenager's home about 8pm on Saturday November 2 to confront him about his behaviour.

When the victim opened the front door, Hardman grabbed him, pushing him against a wall at the base of the stairs and started punching him in the face and body several times before members of the boy's family went to his aid.

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Police prosecutor Sergeant Garry Wilson said as Hardman was pulled away he stomped on the victim's head twice "with considerable force".

The victim sought refuge upstairs in the kitchen and when police arrived, Hardman was still yelling at him, Mr Wilson said.

When questioned by police, Hardman told them he was angry with the boy and "wanted to teach him a lesson".

Defence lawyer Virginia Pearson said her client was extremely remorseful for his actions.

"In hindsight things could have been handled differently ... he has not had the opportunity to apologise," she told the court.

She said alcohol was involved.

Judge Walsh told Hardman his behaviour wasn't acceptable.

"The trouble is you were affected by alcohol ... alcohol and enraged is a recipe for tragedy," he said.

"Stomping on the head was serious. A clear message needs to be sent to the community this is not okay."

He told Hardman the victim had tried to withdraw the charges to help mend bridges between the two.

"It is important you understand he is not to blame. You are the adult. You are responsible."

He sentenced Hardman to complete 100 hours' community work and nine months' supervision with an order to complete a stop violence and drug and alcohol programme.