Jordi Cabot

seriouswp

Once a site starts growing, it always ends up with repeated tags and categories. Sometimes, you create a new category when you were before using a tag. Or you just forget about old tags and en up writing new ones with a very similar name.
This damages the organization your content and the quality of the user navigation on your site.
This plugin helps you to quickly identify (too) similar tags and categories and gives you the option to merge them to simplify your site taxonomies.
In the Configuration page you can define how close term names should be to be considered duplicates.
In the Analysis page you can review the duplications and decide which ones to merge.

Serious Duplicated Terms

Ideal to remove some (quasi)duplicated terms and clean and sort out better your tags and categories

You'll be surprised to see how many duplicated terms you have!

Merge duplicated tags and categories to simplify and better organize the content and navigation of your site

Chris Buck

This plugin deletes duplicate posts from the database, without affecting menus, each time a new post is published. This is an improvement over other similar plugins that would constantly delete custom menus. This plugin works automatically in the background once it is enabled.
The plugin will automatically delete posts with the exact same post title as a previous post, leaving the original post undisturbed. This is particularly useful for when you have syndicated content or auto-posts that result in erroneous duplicates. The original will remain, and all the duplicates will be deleted, allowing you to preserve your page views on the original.

Super Post Cleaner

Deletes duplicate posts from the database (without affecting menus) each time a new post is published.

Serious Duplicated Terms vs Super Post Cleaner