In a large bowl, combine ketchup, brown sugar, Worcestershire sauce, soy sauce, salt, and pepper. Stir the ingredients together until everything is evenly mixed.
Immerse your oxtails in the marinade, making sure they are fully coated. Place the bowl in the fridge and leave it to marinate for at least an hour, or overnight if you have the time.
Heat oil in a large pot over medium heat, then add chopped onion. Fry until lightly browned and fragrant, about five minutes.
Add garlic powder, ground allspice, and dried thyme to the pot. Stir for one minute until the spices are fragrant.
Place the marinated oxtails in the pot and let it sear on each side for four minutes or until lightly browned.
Pour in beef broth, water, butter beans, scotch bonnet pepper, and chopped carrots. Bring everything to a boil, then reduce heat and let it simmer for one or two hours until the oxtails are tender.
Once the oxtails are cooked through, remove them from the heat and allow them to cool slightly before serving.