Daniel Wayne Morton, 19, stood up and told magistrate Richard Funston in Holbrook Local Court on Wednesday he was "very sorry" for his actions, saying he was just "young and dumb".

"Why shouldn't I be locking him up?" Mr Funston asked defence lawyer Mark Cronin.

"Something positive has to come out of this and you must learn from this because if you come back before me again I will lock you up," he said.

"This is not child-like, it is very ugly, adult criminal behaviour - it is sickening."

Morton, who pleaded guilty to commit an act of cruelty upon an animal, was convicted, fined $5000 and placed on a 12-month community corrections order for his part in the attack on the kangaroo at Woomargama in January last year.

Co-accused Holbrook man Shane Price, 21, faced the same court in March and also received a $5000 fine for shooting the animal before filming Morton and encouraging him to attack the injured kangaroo.

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Morton could be seen in the video, which emerged on social media in January, dancing around, imitating a boxer, and punching the kangaroo to the head at least 10 times.

Price could be heard telling Morton to "kick it in the ribs". The injured animal could be seen putting its arms up in a defensive position while being taunted.

The kangaroo died after the attack.

"I was young and dumb and trying to impress my mate but I am trying to get my head straight," Morton told the court before apologising to his parents who supported him during the appearance.

The court heard police believed Morton's actions to be more severe than his co-accused. Mr Cronin told the court his client had "shown remorse" ever since the offence and had handed himself into police after the video appeared on social media.

"You can't put an old head on young shoulders but he made frank admissions to police," he said.

The court heard Morton had made contact with wildlife rescue organisation WIRES and had moved away from his peer group in Holbrook to live with his father in Table Top.