A deadly target used by Filipino knife fighters is to sever the sciatic nerve on the back of the opponent's thigh, high up where it comes down through the pelvic bone. It the nerve is severed, the leg becomes useless.
The femoral artery on the inside of the leg is another good target. If it is cut, the person will bleed out quickly. However, it is difficult to locate and cut during a fight. It is best reached you are on the ground and being attacked.
The iliac artery is the best low section target, accessible with a thrust at the hip joint, it branches directly from the aorta and feeds into the femoral. On the mid section, every part of the aorta is good, but it takes skill, strength, and focus to reach it.
The best high section target is the carotid artery in the side of the neck. A hard cut to the side of the neck may sever the artery and both jugular veins, the internal and external. The positioning of the hand post-cut allows for an immediate follow up cut across the trachea and a stab to the brachial plexus, containing a large nerve and artery.
Cutting as often as possible may be counterproductive. The more a person is cut, the more likely they are to go into a survival mode, fighting harder and ignoring pain.