Google's explanations of obstruction of justice;
Usually a crime must be committed
Lying about a crime to an investigator - Clinton?
Protecting a suspect in a crime - Loretta Lynch?
Destroying or concealing physical evidence in a crime -Clinton?
Investigators and prosecutors can  be charged with obstruction of justice in these cases;
Nonfeasance is the failure to act where action is required, for example not prosecuting when a crime has been committed - Loretta Lynch not prosecuting Clinton?
Misfeasance is the willful inappropriate action or intentional incorrect action or advice, usually by an investigator or prosecutor not following policy with regard to the prosecution of a crime - Comey?
If a crime has NOT been committed;
Malfeasance is a willful and intentional action that injures a party by an investigator, for example implicating someone for investigation with a crime when no crime was committed -  FBI/DOJ investigating Trump for collusion while knowing there was no evidence?