Robert De Niro and Al Pacino have said in interviews that they did not feel proud of the final result of Righteous Kill. They even stated feeling unworthy of their fans' appreciation during the premiere, with Pacino going as far as saying that it is a movie they are both trying to forget. Therefore, both actors agreed that the next project they collaborated in together would be one to be proud of. 11 years later, they were finally very proud and pleased with their next collaboration: Martin Scorsese's The Irishman (2019).
In the first movie where Al Pacino and Robert De Niro starred together, The Godfather Part II (1974), they both played gangsters. In their second movie Heat (1995), Pacino was a cop, and DeNiro was a gangster. In this, their third movie together, they are both cops. This is also the first movie where they have extended interaction. They never shared a scene in The Godfather Part II (1974) and in Heat (1995) they only had two scenes.
Carla Gugino played the sex partner of Robert De Niro in this movie. She played his daughter in This Boy's Life (1993).
The initial cut of this movie ran for two hours, but after a rather negative test screening, Nu Image hastily re-cut the film down to its slender one hour and forty-one minutes to make it more fast-paced and action-orientated. Snippets of some of the deleted scenes can be seen in the trailer.
When Robert De Niro, Al Pacino, and Brian Dennehy are speaking about the murder investigation of "Bob Brady", De Niro says, "Seriously, Lieutenant, how far do you want us to go with this Rambo murder?" Dennehy was the main antagonist, "Sheriff Will Teasle" in First Blood (1982).