Former two-weight UFC champion Conor McGregor says he was "in the wrong" and will "face what's coming" after an altercation in a Dublin pub in April.
Video footage of the incident released earlier in August appears to show McGregor, 31, punch a man in the head.
The Irishman, who announced his mixed martial arts retirement in March, says seeing the video is "like a dagger into my heart".
"I must take accountability and take responsibility," McGregor told ESPN.
"It doesn't matter what happened there - I was in the wrong. That man deserved to enjoy his time in the pub without having it end the way it did.
"I have been making amends to be better - to be a better father, be a better human, to be a better role model to these kids.
"I have to realise that is not the attitude or behaviour of a leader, of a martial artist or a champion. I must get my head screwed on and get back in the game, fight for redemption, retribution, respect - the things that made me the man I am.
"I was completely in the wrong. It was unacceptable behaviour."
Police in Ireland have been investigating the incident and McGregor said: "Whatever comes my way, I will face it. Whatever comes my way, I deserve it. I will face this head on. I will not hide from it."
Asked if he has an anger problem, he replied: "I must be calm. I must be Zen. I must lead by example. I need to get a hold of this and I am working very hard to do this.
"I am taking the necessary steps."
The Dublin incident took place a month after McGregor was arrested for allegedly smashing a fan's phone in Miami, USA.
Florida prosecutors dropped all charges against the Irishman, who had already settled a civil lawsuit out of court.