Trump destroyed the United States' Intermediate-Range Nuclear Forces Treaty with Russia. Without the treaty, Russia and USA can make as many nuclear bombs as they want, as long as they say they will only use them on intermediate-range missiles.

This single action by Trump imperils all of humanity.

https://en.wikipedia.org/wiki/Intermediate-Range_Nuclear_For...

https://foreignpolicy.com/2019/08/02/what-does-the-demise-of...