Michael Adams (mdawaffe)

Just One Category will cause WordPress to display on a category archive page 
only those posts which are direct members of that category, i.e. this plugin 
will exclude from that category page all posts which belong to any of that 
category’s subcategories but do not belong to the category itself.

Just One Category

On a category's archive page, displays only the posts directly in that category, not in any sub-categories.

Marios Alexandrou

Ultimate Category Excluder, abbreviated as UCE, is a WordPress plugin that allows you to quickly and easily exclude categories from your front page, archives, feeds, and searches. Just select which categories you want to be excluded, and UCE does all the work for you!

Ultimate Category Excluder

Ultimate Category Excluder allows you to quickly and easily exclude categories from your front page, archives, feeds, and search results.

Just One Category vs Ultimate Category Excluder