President Garrett Walker
How he got Underwood-ed: Frank set the POTUS up to fail at every turn, exposing marital secrets, linking him to corruption he was never a part of, and throwing him to the DOJ wolves.
The result: Preemptive resignation before impeachment
How bad should we feel?: Relatively bad. President Walker was boring, but he was one of the few good guys on the show, a politician who actually played by the rules and wanted to do right by the American people. Now his legacy is that of Nixon 2.0.