Strike on vital points can be fatal. Hands up balancing body. The knee is an excellent midrange tool if used in conjunction with the hands to immobilize and then attack. The knee must be snapped up from the strength of the abdominal muscle groups. It should not be swung up as a pendulum.
Steps are firm.
The strength comes from foot rooted to the ground, never let your attempt be known. Power of a tornado. Too often, the novice in an attempt to gain more range or elevation in their kicking techniques will violate the root from their support foot by coming up on the ball of the foot. It is imperative that there exist a strong anchor from which to rebound the kinetic wave, or much of the energy potential will be scattered. This is one of the reasons this skill is so heavily emphasized in my family's training curriculum.