A two-time first-team All-Pro and a four-time Pro Bowler, he won two Super Bowls with the San Francisco 49ers.

He grew up 20 miles (32 km) east in Ruston, where he attended the all-Black, segregated Lincoln High School.

[2][3] Dean was a standout at Louisiana Tech University in Ruston, having spurned an opportunity to play for legendary coach Eddie Robinson at nearby Grambling State University, which at the time was sending African American players to the NFL on a yearly basis.

Chargers coach Tommy Prothro initially projected him as a linebacker but eventually relented to Dean's wish to remain a lineman.

In 2013, U-T San Diego called the Chargers trading Dean "perhaps the biggest blunder in franchise history".

[22] After only a couple of practices, he played and was still able to record two sacks and apply pressure and repeatedly hurry Danny White in a 45–14 win by the 49ers.

His performance was noted by author Tom Danyluk as "the greatest set of downs I have ever seen unleashed by a pass rusher".

[26] The 49ers went on to win Super Bowl XVI that year, and Steve Sabol (NFL Films) is quoted in 2006 as saying that Dean's acquisition was the last meaningful in-season trade, in that it affected the destination of the Lombardi Trophy.

[29] Dean was inducted into the Pro Football Hall of Fame in 2008,[28] when his bust, sculpted by Scott Myers, was unveiled.

[37] Dean died from COVID-19 while being airlifted from a hospital in West Monroe, Louisiana, to Jackson, Mississippi, on October 14, 2020, during the COVID-19 pandemic.

[1][38] Dean is one of at least 345 NFL players to be diagnosed after death with chronic traumatic encephalopathy (CTE), which is caused by repeated hits to the head.