after St. Louis police unions instructed officers to publicly display The Punisher's insignia (the mark of a lawless, fascist murderer) the comic book community was quick to point out the stupidity, and the frankly horrifying message sent by supposed peace officers endorsing a maniac. So it's a good thing The Punisher personally confirms he hates cops who see him as a friend… making every cop who "wears his mark" or calls themselves a "fan" look like shameful fool in the process.
-- Andrew Dyce, The Punisher Confirms: He HATES Cops Who Support Him
There's a saying I first heard from cops in my country and then later saw pop up in several TV shows, the last one clear in memory being The Rookie.
The saying embodies that whenever cops decide to group together to the point of getting a symbol or name for said group, it's only a matter of time before they go to jail.
In corrupt countries, they may not actually go to jail, but the point is that whenever cops do this, criminality will always ensue.
I don’t know where the US fits in your consideration of corruption but cops very rarely go to jail here, even (especially?) when they form up around a symbol. Here’s one example: the long-lived murderous LA Sheriff’s Department gangs. https://knock-la.com/tradition-of-violence-lasd-gang-history/
The point is that when they label themselves with a symbol or name, they up to some criminal shit already or before long.
And yes, sections of US police are corrupt as cops get away with murder on a daily basis.
Corruption doesn't need to mean they are on the take (although there's probably plenty that are), it can also simply mean that they turn any level of blind eye for their own or external groups.