Sputnik was cool. Stealing US nuke designs was pretty based. Part of the problem is many Soviet secrets are now NATO secrets.

They also invented an OWP (which thankfully they did not deploy) and a way to monitor weather by satellite at the poles. (That is to say they developed a usable alternative to geostationary orbit to keep a satellites over a spot on the Earth. NASA uses their method today)

Also the Ruskies were the first ones to think Maybe we should find a way to get along with the capitalist imperialists.