The opposite of the forward stroke is the back stroke.  We often use this stroke to slow down and stop.  Back strokes are also used when performing back ferries.  The stroke starts with the paddle flat on the surface rather than the stabbing entry used in the forward stroke.  This provides extra stability.  From this point on it is very similar to the forward stroke, just in reverse.

This is an excellent video on the back stroke from Mike Aronoff at CKAPCO: The Back Stroke.

This short article and video from REI covers all the basic strokes with the back stroke at the end: Basic Kayak Strokes.