Anarchists winning the Spanish Civil War
I have such a soft spot for the Anarchists that I want them to succeed.
However, IOTL they pissed off the right by looting churches and abusing the clergy and pissed off the Socialist government by staying autonomous, maintaining separate militia and so forth. The Republic's fate was sealed by a mixture of infighting between the Popular Front and the Anarchists and the Western arms embargo. Once they took Soviet aid, they were anathema to Western support.
A possible POD to allow Anarchist survival would be more unequivocal support by Leon Blum and the French government in 1936. (IOTL they sent very tepid support to the Republic not to antagonize the right in France) sending a lot of French volunteers to fight, as well as giving the French military a clinic of how to deal with blitzkrieg so they wouldn't get caught quite as flat-footed as they were IOTL. If they learned any useful lessons, as the Soviets did, it would have given a whole different flavor to the Phoney War.
As an American Francophobe, that's distasteful, but the only semi-viable option I can think of to prevent the intramural bloodletting between the Socialists and Anarchists to please the Soviets. The Americans were NOT going to back a Communist government. However, they might not have been so vehemently against a democratic government with French backing.
OTOH, the domestic fallout from accepting French help (shades of Bourbon occupation, part II, I can see the Falange propaganda posters now--) might have put the Caballero-Azana governments in an even bigger bind than IOTL. If the Anarchists couldn't organize a pissing contest in a brewery, the Spanish Socialists couldn't sell ice in Hell at home or abroad.
My 2c on the subject anyway.