17. Michael Vick
Vick redefined the quarterback role during his time with the Falcons. It appeared as though he was a future Hall of Famer. But then he served two years in jail after a federal investigation into a dogfighting ring. Vick was the ringleader.
It rocked the NFL because it was such a horrible crime. Furthermore, the details disgusted animal lovers across the world. Vick joined the Eagles after he left prison and still had some productive seasons. But he was never at the same level (via MARCA).