There is no crueler tyranny than that which is perpetuated under the shield of law and in the name of justice. ~ Montesquieu
Police corruption and brutality are dark stains on any government which tolerates it, as these are most profound violations of rule of law. That stain is upon practically all countries.
The brutality of American police is by no means novel. In much of the world, police are not much more than thugs sanctioned by the state. Corruption is tightly woven into the social fabric.
Police brutality is as common as water. ~ Nigerian human rights activist Justus Ijeoma
In general, the more murderous the country, the more deadly its police. American cops shoot more mostly because more people shoot at them. They are 36 times deadlier than German police officers, but also 35 times likelier to be killed on the job.
In many countries, the authorities encourage extrajudicial executions, either to suppress crime or to get rid of dissidents. Voters often applaud them for it. Such as been the case in recent years in the Philippines, Thailand, El Salvador, India, and Pakistan.
Men with a feeling of entitlement to authority are naturally given to violence when frustrated, especially when accountability is sorely lacking, as it is so often with police. As America illustrates, lack of social cohesion and biases inflame the potential for brute force. American culture is crude in its celebration of violence, as are many others.
Unlike other governmental agencies, law enforcement has violence at its instant disposal. Lethal force makes police corruption particularly potent.
There is another unique aspect to the police. They are the domestic enforcement arm of the state. Their essentiality means that the state never emasculates the police force. On the contrary: police are empowered to suppress dissent when the state feels threatened.
The police are the public face of the state. Their behavioral norms are the beating heart of the state, and by that token signify the soul of a society’s morality.
What are the police powers of the State? They are nothing more or less than the powers of government in every sovereignty to the extent of its dominions. ~ SCOTUS in License Cases (1847)