To delete paperclip attachment

users_controller.rb

def remove_image
  @user.image.clear #This is optional you can skip it
  @user.image.destroy #This line delete image from paperclip
  # Now you need to update image url because destroy is not remove url so you need to update image field
  @user.update_attributes(image: nil)
end
#Note: You can directaly update your image field but it doesn't delete image from storage.
#Note1: Controller name may be changed according to your requirement.