The answer to 'how to kill wasp' is to use an insecticide spray specifically designed for wasps. Spray the nest directly, aiming for the entrance, and retreat to a safe distance. Avoid approaching the nest directly, as wasps can become aggressive when their nest is threatened.
For best results, spray the nest in the evening or early morning when wasp activity is lowest. Repeat the treatment after a few days to ensure the nest is eliminated. If the nest is located in a difficult-to-reach area or the infestation is severe, it's best to call a professional pest control technician who can safely and effectively remove the nest.