What is the best TKD kick?

The best Taekwondo kick to use, as of self-defence should literally be a spear hand thrust so the person or opponent backs of, and then if the person comes back in order fight, you must launch a 540 kick in the face. This can make someone feel really unconscious. But the best thing I would do if I didn't know how to fight back, was that I would join Martial Arts classes just in case I needed a process of fighting sequences.