helpgeek

By default, the built-in Recent Posts widget in WordPress only allows you to 
display up to 15 recent posts max, even if you specify a larger number. This 
is hard-coded into the WordPress core so any modifications you make would have 
to be redone upon every WordPress update.
No longer!
The Recent Posts Widget Unlimited functions exactly as the built-in WordPress 
widget but without the 15-post restriction. You can now specify an unlimited 
number of recent posts to display without resorting to modifying the WordPress 
core.

fervillz

This plugin will empower a custom, adaptable and easy to use recent posts widget, you can show it by means of widget. Permits you to show a list of the latest posts with thumbnail, excerpt and post date.

Good plugin for all languages

Gives adaptable and highly organized recent posts. Show it through widget with thumbnails, post excerpt, post date.

Recent Posts Widget Unlimited vs Recent Post Widget Thumbnail