So ...

We are going to use a handy widget called Top Commentators Widget.

Here it is:

https://wordpress.org/plugins/top-commentators-widget/

It's a very small widget (9 KB), but let's see the usual speed tests ...

Here are my results before installing the plugin ...

... and the result after installing and activating the plugin:

No more comments needed ...

So, let's see how it works ...