The linebacker with the most sacks in an NFL season is Justin Houston of the Kansas City Chiefs. He finished with 22.0 sacks in 2014.
Elvis Dumervil of the Denver Broncos. He had 17 sacks.
There isn't really a record kept for fewest sacks in a season by a player, as there are thousands of NFL players who have not had any sacks. Michael Strahan holds the record for most sacks in a season, at 22 1/2.
Through 12 games of the 2012 season that is DE Aldon Smith of the 49ers with 17.5 sacks.
Mike Berg of the Green Bay Packers had 9 sacks in the 1979-1980 season.
Unfortunately, Karras retired after the 1970 season. The NFL did not begin recording sacks officially until 1982.
Jared Allen
DeMarcus Ware of the Dallas Cowboys with 20.
That was 2004. He led the NFL in sacks that season.
For last season it was actually DeMarcus Ware who had 15.5 sacks. Cameron Wake was third with 14 sacks behind Tamba Hali at 14.5.
In the 2007 NFL season, there were 1102 total sacks so the average team was sacked 2.2 times per game (34.4 times per season). In 2006, there were 1164 sacks averaging out to 2.3 sacks per game per team (36.4 sacks per season) and in 2005, there were 1182 sacks averaging out to 2.3 sacks per team per game (36.9 sacks per season).
Julius Peppers is the career leader in sacks for the Carolina Panthers. Thru week 5 of the 2008 NFL season, Peppers has amassed 59 sacks in his career with Carolina.