Removes tags with only one article from the tag cloud widget.
Can be combined with the <a href="https://wordpress.org/plugins/redirect-single-article-tags/" rel="ugc">Redirect Single Article Tags</a> plugin.

No Single Article Tags in Tag Cloud

no settings, a clear goal - exactly what i needed

Does what it says!

Removes tags with only one article from the tag cloud widget.

Waterloo Plugins

Tag Cloud Widget adds a simple tag cloud widget that you can use anywhere on your blog. This plugin looks at all your tags and displays them in a widget. The more times a tag is used, the larger the tag is.
Each tag is a link to the tag page (e.g. http://your-site.com/tag/your-tag). This will help with SEO.
Currently, there aren’t any options to customize the tag cloud. It should work well out of the box. In the future, there may be options to customize the widget.

Good

A tag cloud widget with links to your tag pages

No Single Article Tags in Tag Cloud vs Tag Cloud Widget