The answer to 'how to kill wasp' is to use a wasp and hornet spray. Wasp sprays contain insecticides that can quickly kill wasps on contact. Spray the nest directly, aiming for the entry points, and avoid spraying at night when wasps are less active. Be cautious when approaching the nest, as wasps can become aggressive when their home is threatened.
If the nest is located in a hard-to-reach area or you're dealing with a large infestation, it's best to call a professional pest control technician. They have the proper equipment and training to safely remove wasp nests and prevent future infestations.