You can kill both Rax and Max in the Maliwannabees mission in Borderlands 3. There is some good news here, as it does not matter which one you kill because you can kill both. That's right, after you kill either Rax or Max and leave, Ziff will give the dialogue equivalent of a shrug and suggest you kill both.

Who did it Rax or Max?

Due to the supply vehicle being on fire, it is more than likely that Rax is the true killer. Inspecting it further offers no more clues, after which Ziff claims she doesn't care who the player chooses to dispose of. Here players can decide to kill one, the other, or both.

Who killed ziffs family?

Ziff's family were murdered by a pair of bandits on Promethea.