You can delete a category with REST API in Magento 2 with rest/V1/categories/:categoryId
Action: DELETE
URL: <WEBSITE_URL>/rest/V1/categories/:categoryId
(Example: https://magento245.test/rest/default/rest/V1/categories/10)
Header: Authorization Bearer <ADMIN_TOKEN>
Payload: Empty
Response: Boolean Value.
You can delete any category by id in Magento. Just need to pass the correct category id in the Request URL.
Need to pass Admin Token in the Header to delete a specific category.