The guy at the top, controlling the drop and making the heavy containr drop slowly, is doing negative work.
He's exerting force upward ... opposite to the direction the container is moving. So the product of (force) x (distance) is negative. He's controlling the potential energy that the container had when it left the second floor, and making sure that the container reaches the ground with zero kinetic energy.
-- The guy in the window holding the rope is doing negative work.
-- Gravity is doing the positive work.
