When the Millennium falcon jumps to lightspeed at the end:
VADER stares out the window. He turns away, uttering under his breath, "No." He glances back out the window. As he turns again to walk away, he lets out a bellowing "NOOOOOOOOOOOOOOooooOOOO!"
This would serve to dissolve all tension in this scene, even more so than the scene where this actually happened.