Derek Brown

Overall
Derek is a well known hit man and assassin, he's completed many contracts and has made a lot of money doing. Though his ego and greed usually get the better of him.

Derek eventually betrayed Tony and attempted to kill to cash in his bounty, be he was killed by Barney during one of his attempts.

Homeless Millionaire
Derek was introduced early in the story after Tony helped him out of some trouble with the cops. They later began to work together and made a pretty penny doing assassin gigs. Derek was brought on by Chernov to do a gold heist after that Derek began to work more with the crew.

When Gary Boyle attacked the crew Derek was their man in the city and he told them that Boyle had a Data Center that they could hit in order to set back his plans. So Derek, Tony, Barney, and Chernov helped out in the assault and eventually destroyed the building. After this Derek was captured by Gary Boyle and was offered a deal. He was being paid one million dollars to take out Tony.

Derek attack Barney and Tony when they were selling some shoes and he began to shoot at them with a sniper. Derek was forced to retreat due to a raging fire in the woods. Derek later got the drop on Tony at the fire department and had Tony wounded and pinned. But Tony called Barney in to somehow help and Tony managed to stall Derek long enough for Barney to arrive. Barney threw an explosive shoe at Derek's sniper tower blowing up the tower and him inside.