If you were using your empty hand, you would kick in the long range, and closing the range you would punch elbow,knee, headbutt, and then move into grabb & tear, (pluck), direct application of pressure to nerves, or redirect the motion of your body or your opponent body to cause your opponent to impact on a hard object causing severe damage.
The considerations for a blow or a tear would be as follows: Reaction time - Can you do it before your opponent will put you in any kind of immediate danger? Also can you use your move to cause distraction to your opponent and buy few split seconds to achieve your planned tactics?
Range - Is the range facilitating sufficient acceleration and momentum for the body part or weapon you are using?
Finally consider using either your arms or legs or the weapon or combinations considering the all of the above.