Most coaches will not think that the forehand underarm drive as an important shot to be learn or practise upon. This shot is as important as the drop shot in badminton.
One of the common mistakes when hitting a forehand underarm drive is that most players tend to use the full swing motion while hitting the shuttle.
The forehand underarm drive is used when a player return a shot to the opponent when the shuttle is already lower than the net.
If you can do this shot properly, treatment one can add some deception into the shot. There are many variety of shots that you can make if you hit the forehand underarm drive. Straight lift, cross court lift, straight drop or even the cross court drop can be done thus making your opponent guess the location of your next shot.
In shot, all angle of shot can be made. Watch this video to learn the exact way to hit the shots.