The 19-year-old victim, who had moved overseas after studying in Dunedin last year, said the episode had changed her life.
Appearing at the hearing by video link she told the court she had isolated herself in the aftermath and used alcohol and drugs to numb the pain.
"For a long period I didn't sleep because all I could feel was your skin and your breath against my body," she said.
"The memory of this night still haunts me."
She was at a bar in the Octagon with friends on July 25 last year when she made eye contact with McNeill in the smoking area.
He immediately approached and complimented the teenager on her appearance.
She thanked him, but McNeill's intentions soon became clear.
"You reached out without hesitation and grabbed her breast with one hand then moved your hand down to her genital area," the judge said.
McNeill told the woman he wanted to have sex with her.
The victim said she had a boyfriend and promptly left the bar with friends.
"I concluded you saw an intoxicated young woman and took your opportunity to deliberately offend against her," Judge Glubb said.
McNeill, the court heard, had previous convictions for drugs, drink-driving, dishonesty and disorderly behaviour, but had no sex crimes on his record.
Counsel Brendan Stephenson said his client wanted to emphasise "the impact these proceedings have had on him".
He said McNeill's mental health had declined to the point where he was unable to work at present.
The victim told the court she had spent months blaming herself for what occurred.
"I told myself over and over I could've done something," she said.
"I still have nightmares but feel safer in the knowledge I received my justice."
McNeill was sentenced to four months' community detention, 80 hours' community work and was given a first-strike warning under the three strikes legislation.