The money?
It looks like he never got the money! Another macguffin?
shareSPOILERS
I think the deal Chicago mob boss Eddie Egan offers Lee Marvin is "anything goes." Implied: get the money, or kill Hackman and destroy his mob.
Marvin opts for the latter. "One way or the other." Marvin lets Hackman survive the movie, but it looks like Hackman is mortally wounded to me. But even if Hackman survives, his brother Weenie is dead and the mob is crippled, and likely Hackman is going to be crippled, too.
I suppose leaving Hackman alive left the door open for a sequel that never happened...