-FEC violations (hush money)
-Emoluments clause violations
-Obstruction of justice (multiple counts)
--Suborning perjury, witness tampering
-Failure to uphold oath of office
-Improper granting of security clearances
-Tax fraud
-Misappropriation of federal resources
-Serial ethics violations
-10,000 lies and counting
-Conspiracy to defraud the US (collusion) (SC suggests case could be made with sufficient time, resources, efforts to get truth from witnesses)
-Human rights, federal violations at the border
Much else that he has done could be interpreted by Congress as impeachable--attacking Constitutional protections for free speech, attacking Constitutional role of Congress, etc.