In my eyes, Lombardi's best free agent signing in his 6 years here.
Not signing Kovalchuk was #1.
Mitchell and Scuderi made it possible to ice 3 young defensemen at the same time, both were great signings. They were rocks for the defense. Even Greene was a solid 3rd pairing defenseman in the playoffs and a rock on the PK.
The Kings' corps of defensemen top to bottom is one of the best assembled in the NHL over the past 10 years. Most teams need to hide a defenseman or two, or keep them away from certain matchups, but with the Kings' d-corps Sutter didn't really have to do that.