I'm not too familiar with the Korean or Greek ones, Russia and mexico are pretty spot on but idr Zapata's exact politics, I get the revolutionaries mixed up but I think he was kind of a mess?
The Spanish context might've been unwinnable even if Stalin had cooperated fully. Russia was kind of a shit show as far as military and industry, and couldn't handle all of Germany+Italy's direct aid from next door while navigating all of it through hostile liberal states. Maybe they could have if they hadn't spent all their time doing internal purges and being run by a dipshit gangster, but that's being generally internally shitty, not being a bad ally.
Like they did fuck it up, sending commissars and shit, but I'm not sure it made the difference.