ACAC, you can't say you're a good one if you see wrong-doing from fellow officers and do nothing about it.
guy 1: hey did you hear the victorian police shot a 15 year old with a knife?
guy 2: yeah, ACAC mate.
ACAC is an Australian saying and known song in which has been around since the 70's stating "All cops are cunts" similar to the ACAB. The All cops are cunts song only consist of the lyrics "all cops are cunts."
child: "Hey dad look the police are coming!"
dad: "ACAC"
child: "whats that?"
dad: "It goes: all cops are cunts, all cops are cunts, all cops are cunts."