The great El Lissitzky, 1919
The also great Rodchenko
The two above and more from Soviet Cinema here
Above from International Poster
Rodchenko again, seen all over.
Stenberg for Potemkin, very nice
This from a painter, Lebedev, seen here.
Two above, from here, are particularly upbeat.
There is a fine book about soviet posters, called just that, see here