Oliver Platt as R.D.
R.D. (a.k.a. Reese Dipple) is an extremely private and conservative client worth billions of dollars. Dipple hired Diane Lockhart to argue the liberal side of a mock case and eventually brings his business—and his lawyer, Ethan Carver—to Lockhart/Agos/Lee.
See the man behind the notorious moniker in "Red Meat" on CBS All Access.