He is an homage to Archie Goodwin in the Batman Adventures stories in which he originally appeared.
At one point Mr. Nice proves his niceness by giving the bank truck guards money because they needed it.
This version appears as an assistant to the penguin and it is unknown if it is the same as the Batman Adventures character.
Unlike the Batman Adventures character, Jimmy Nice was responsible for the death of his partner/lover which led to him going insane.
Major Story Arcs
Robin: To Kill A Bird
While in Blüdhaven, Mr. Nice works for the Penguin and holds the nightly business meeting. He has a clip board with all the items to discuss. Item 10 is a journalist who has rebuked the Penguin's presence in Blüdhaven. Mr. Nice suggests having the man killed, but Penguin decides to have journalist finger chopped off and left near an emergency room.
In Rebirth, he is head of the rehabilitation center helping former criminals. He is later revealed to have been responsible for the death of his partner and framing of the Run-offs for the killings in the city which he committed. He is defeated by Nightwing, Defacer and Detective Svoboda and arrested for his crimes.