Answer:
I believe a president should be impeach when the President fails to complet his civil duties as president. And the lack and radical decision making. For example, Andrew Johnson whole motive in impeachment was the reason that he was accused of violating the Tenture of Office Act and try to fire the Secretary of War a republican from Licoln Cabinet. Tenture Of Office Act is the restriction of Presidential power to remove any certain office holder without consulting the Senate (the highest House). Another example, would be Bill Clinton with the accusation of perjury which is when under oath uses any falsely material shall be appointed guilty. And last but certainly not least, Donald Trump was impeached by "incitement of insurrection" which occured on January 6 when his followers attacked the U.S capital. Which was seen as a terroist act (i mean it sort of was...)