It is very simple and easy to do.

Simple Way

You can simply open the console in your Google My Activity section and paste this short code:

document.querySelectorAll("[aria-label*='Delete activity item']").forEach(button => {
    button.click();
});

Make sure to leave the tab open for a few minutes to ensure all delete requests are processed by Google.

Explanation

The code selects all elements with an aria-label containing ‘Delete activity item’ and clicks each one to trigger the deletion of your comments.

This automates the process, saving you from manually deleting each comment.