Not in Spain. The anarchists (ironically I suppose) were the most organised, along with the social democrats of the PSOE. Stalin ordered that the equipment sent from the Soviet Union only go to the communists, although even that was limited compared to the support given to the rebels by Hitler and Mussolini. The communists spent much of 1937 undermining the anarchists and other non-Stalinist socialists, even risking collapse of the frontlines in Catalonia and around Madrid by withdrawing troops to attack their supposed allies. This culminated in the "May Days" in the anarchist stronghold of Barcelona.
As for Southern Europe, especially the Balkans, I'm only aware of the Yugolsav partisans being a successful and ostensibly communist organisation, although many of Tito's partisans weren't communists. Tito himself was extremely distrustful of Stalin, resulting in cooperation with and resceiving support from the Western allies.
Biting the hand that feeds IT
