Thanks again Kelerei for your kind reply.
I have notified my friend.
He said he got his first residence visa while in NZ 6 yrs ago.
His timeline as follows
2013- came on visitor visa
2014- work visa
2015 (May) - First residence visa
2016- First DUI
2017- Second residence visa ( he went through that DLN process and applied for subsequent RV)
2020- Permanent Residence Visa
2021 - He applied for NZ citizenship
2021(July) - got charged with domestic violence ( his case is in progress)
His lawyer told him the same that there will be some issues in getting NZ citizenship which totally depends upon what sentencing he will receive for his new offence.
His duty lawyer also mentioned that since this is his fist offence under that category, he might not get jail sentence but may get a conviction.
Thanks heaps.