Abidemi Kusimo

You can make use of category popular tag to display most used tag on your blog. This will give list of frequently used tag anywhere you place the shortcode or funtion in your theme.
For example [popular_category_tags count=10 type=”popular-tags” category_id=”1″]. 
You can also call this function from your theme file: cush_category_popular_tag() for basic output.
When using the shortcode type is required. category id, count is not required. if no category id suplied, the plugin will default to current post category available. 
For example [popular_category_tags type=”popular-tags” ].
You can find category tags options under Settings page 
Settings -> Category Tags
Credit : (https://wordpress.stackexchange.com/questions/261617/display-most-popular-tags-of-category)

Category Popular Tags

Display popular tags on achieve/category page of your theme using sortcode or by calling a function.

Julio Potier

IMPORTANT: 3.0 supports cahing plugins!
When someone visits a post or page (not a search engine bot crawler), it adds 1 count views to its counter.
But this is not all, the counters are split in days, weeks, months, years, so you can see stats and display any stat day.
Then you can display this views with the provided shortcode [post_view] or use the widget to display a top (or less) posts list.
You can also use [most_view] in a post/page to get a top (or less) post most viewed.
If you were using another kind of plugin before and don’t want to lose your counters, this plugin can keep them!

Post Views Count (Support caching plugins!)

This plugin counts views for post and pages, shortcodes [post_view] & [most_view] are available, also a widget "Most Viewed Posts" is.

Category Popular Tags vs Post Views Count (Support caching plugins!)