The Hoare-Laval Pact isn't leaked and the Stresa Front remains. The Stresa Allies go to war with Germany in 1937 or 1938.
As Britain, France, Germany, and Italy are preoccupied, Stalin sees a brief window to take action. He proceeds to go after Poland, Romania, Finland, and Turkey.
As Germany is facing sure defeat in the face of the Stresa Allies, Stalin goes after Germany east of the Oder River. All German lands seized are given to Poland, because Stalin is such a nice guy.
The Baltic States are threatened with war, but agree to acquiesce to Stalin's demands which amount to Finlandization at best and being Soviet Puppets/Buffers at worst.
Stalin also revokes the Svalbard Treaty, claiming the whole archipelago for mother Russia.
Hungary tries to grab a piece of Romania, but Stalin responds by invading Hungary.
Czechoslovakia here is a pure neutral.
By the time Western Europe is at peace, Stalin controls half of the continent. Stresa + Germany is facing down the Soviets and the Americans are on the other side of the ocean eating popcorn.