godthor

This will create a new widget which will display your most popular posts and pages based on comment count with Disqus. Alternatively, you can use a shortcode as well.
It’s very simple to use. Just drag the widget into a sidebar and configure it, or visit the settings under the WordPress Settings menu.
Just Some of the Options:
<ul>
<li>Show featured image.</li>
<li>Choose featured image size.</li>
<li>Choose featured image alignment.</li>
<li>Show the post date.</li>
<li>Select how many days to check, IE: past 90 days.</li>
<li>Set how many posts to show.</li>
<li>Save the results for faster loading.</li>
<li>Load results using Ajax. Perfect to avoid caching results.</li>
</ul>
Note: This plugin requires you have an application registered with Disqus: https://disqus.com/api/applications/ 
It’s free and simple to setup, just follow that link.

Disqus Popular Posts

Creates a widget to show the most popular posts and pages on your site based on Disqus comments. Can also be used with a shortcode.

pipdig

This plugin will remove any of the default WordPress comments features from your site, and replace this with Disqus.
Please note: Disqus comments will not be automatically imported into your WordPress dashboard. Instead, you can continue to moderate your comments via your Disqus moderation page. This plugin will add a quick link to your Disqus moderation page in the WordPress Admin Bar.
Reasons to use this plugin:
<ul>
<li>Simplify your WordPress dashboard by removing the “Comments” admin menu.</li>
<li>Easy setup: simply add the Disqus shortname in the settings and you’re all set.</li>
<li>Comments are NOT imported to WordPress – save server resources and database size.</li>
<li>Improved spam protection to keep junk out your site’s database.</li>
<li>It has a silly name.</li>
</ul>
This free plugin is brought to you by <a href="https://www.pipdig.co/" rel="nofollow ugc">pipdig</a>

pipDisqus – Lightweight Disqus Comments

A lightweight solution for adding Disqus to your WordPress blog.

Disqus Popular Posts vs pipDisqus – Lightweight Disqus Comments