How do you unlock every character in resident evil 4

To unlock every character in Resident Evil 4, perform the following:

Ada Wong: Get a four-star rating in the Pueblo map of The Mercenaries
Jack Krause: Get a four-star rating in the Castle map of The Mercenaries
Hunk: Get a four-star rating in the Island Commando Base map of The Mercenaries
Albert Wesker: Get a four-star rating in the Waterworld map of The Mercenaries