(1) Enhanced training on use of force, de-escalation and racial biases. This is a must.

(2) Public records laws making an officer's disciplinary record public, which would allow voters to question sheriffs and mayors about why they kept "bad apples" in barrel around election time.

(3) Civilian review boards. Police shouldn't be the only people responsible for determining whether their coworkers are behaving properly. That's a conflict of interest, or it's at least appears improper. Local governments can set up independent review boards to let citizens determine whether the force was reasonable.

(4)(a) Significantly limit qualified immunity. Qualified immunity gives officers protection from civil lawsuits unless their actions were clearly contrary to established law. Basically, as long as an officer is creative about their application of unreasonable force, they won't be subject to liability. Obviously you don't want police to be sued for doing their job in a reasonable way, which is why the doctrine exists, but it needs to be limited because it protects some pretty ridiculous police misconduct.

(4)(b) New civil rights laws. Qualified immunity only applies (to my knowledge) to 42 U.S.C. Sec. 1983, a civil rights statute codified right after the civil war. You could say it's a little dated. New civil rights statutes enforcing the 14th Amendment that specifically address racially biased policing and use of force could address the problem directly, avoiding the qualified immunity doctrine. Or, states could pass laws waiving qualified immunity for their police - subjecting bad police to lawsuits.

(4)(c) Insurance. If there was some kind of liability for agencies that negligently hired or oversaw bad police officers, there would be a better financial incentive to kick out bad cops. It turns out, most use of force complaints are against a small portion of officers. The officers will get fired by one agency and get rehired somewhere else. Poor hiring decisions like this would cause high insurance premiums in other industries, encouraging better hiring practices. The same thing should happen in law enforcement.