This is not an easy answer, but here goes

Law enforcement should have nationally standardized basic education requirements which states can expound on but not reduce.

This education should cover and emphasize de-escalation, comprehensive basic sociology(including racial and gender equality), psychology, abnormal psychology, crisis/conflict resolution, basic medical/first aid, as well as the current tactical training they already receive. In whole academies should be much longer than the 9 week national average. Make a national certification test for academy graduates must pass before entering full time service.

Mandate psychological evaluation and background checks before allowing entry into academies. Periodic psychological check ups and mandated independent counseling after high intensity events or when complaint investigations determine that the officer is operating outside of department guidelines.

Limit unions abilities to shield officers that repeatedly violate policy and have zero tolerance policies for class B misdemeanor offences and higher. And cannot allow departments to rehire officers with out some sort of reconciliation or rehabilitation.

We as a society expect a lot from local law enforcement. We either need to give them the tools they need to do all the things we think they should do, as an attempt to limit the risk of bodily damage or death to themselves and civilians. Or we limit the scope of what they do and employ other types of officers that handle non violent, non criminal activity. Communities need to get together with city and state officials at like an ongoing round-table to communicate the communities needs and concerns; then adjust action plans to best meet them.