Carlson is an average guy. He is a farm hand working on the ranch, just like Slim, George and Lennie. Carlson does not have any obvious failings like Lennie and Candy, but he does not have any obvious skills or advantages like Slim and George.
Carlson, then, is an average man.
Like Curley, Carlson is also violent. Carlson is average in a rather violent and unfeeling world.
He is insensitive, brutal, violent, and fanatical; his only contributions to the group are destructive.
In the story, his character is involved with two episodes of violence, allowing us to describe Carlson as being somewhat prone to violence. (Where his rage comes from is not entirely clear, but probably has something to do with his status as "just an average guy".)
The episodes of violence concern 1) the shooting of Candy's dog and 2) the manhunt of Lennie. In both cases, Carlson is prepared to take life. In one case, he does.