1) Ordering military attacks on sovereign nations without Congressional authorization.
2) Issuing Executive Orders for the extra-judicial assassination of U.S. citizens in violation of guarantees of due process.
3) Presiding over military, paramilitary and intelligence service use of torture in violation of prohibitions against cruel and unusual treatment.
4) Ordering and attempting to assassinate foreign heads of state.
5) Obstructing justice by failing or refusing to investigate credible allegations of torture brought against the previous administration.
Many, Many more reasons.