4. Aldon Smith
Smith had an unbelievably high ceiling. He achieved 14 sacks for the Niners in his rookie year but never started a game that year. As a sophomore, he went even further. This time Smith broke the franchise record for most sacks in a season with 19. It looked like they had a future Hall of Famer on their hands but it wasn’t to be. Smith’s personal issues cost him his career and broke the hearts of fans.
In 2012, police arrested him for a DUI. Nobody condones that kind of behavior but people make mistakes. Unfortunately, this wasn’t just a one-off. The Raiders gave him a second chance but Smith committed domestic violence. Then, he became involved in a domestic battery case and that ended his career (via NBC News). Fans saw his potential but he didn’t have the discipline to make the most of it.