Ajax response from controller file Magento 2

To Pass ajax response from the controller in Magento 2, You need to use Magento\Framework\Controller\Result\JsonFactory Object.

Magento\Framework\Controller\Result\JsonFactory used for sending a response from a controller to ajax request.

Pass your response in setData() method.

From Js/Template file which place you have called Ajax Call, You can get Response as html and success parameter from an above response.

You can manage your Response from controller file.