How to Show Only Popular WordPress Tags in WordPress

First of all install and activate Simple Tags plugin on your site. It gives you full control over the tag.

After activating the plugin, click on Appearance >> Widgets page and drag-drop the Simple Tags widget to your sidebar.

It will expand automatically. Here you can select the number of WordPress tags to be shown, font sizes, colors etc.

After making the settings as per your requirement, click on the Save button.