There are two different ways in which you can delete transformations:
1. The Media Library - via the transformations page.
2. The Admin API
When using the API, you can delete the transformation in one of two ways:
Delete transformation by name -
Delete transformation by parameters -
Cloudinary::Api.delete_transformation(:width => 150, :height => 100, :crop => :fill)
Please note that deleting a transformation also deletes all the derived images based on this transformation (up to 1000). The method returns an error if there are more than 1000 derived images based on this transformation.