Stalin very publicly turned against Tito when it became obvious he couldn't be pushed around easily (wouldn't agree to extremely unfavourable trade deals, wasn't happy with the idea of joint-investments in Yugoslav industry that would've effectively turned them over to the USSR, and more). This ultimately lead to Stalin and the USSR-aligned countries denouncing him, despite originally being very close with newly socialist Yugoslavia. I think this was a really tough one for Tito - he'd spent time in Russia after the revolution, sought out Soviet help during war (without really receiving any) but for a while truly believed the USSR could've spearheaded a global socialist movement.
Tito and Stalin didn't see eye-to-eye. There was complete split after the WWII. Soviets blockaded Yugoslavia and Yugoslavia was included in Truman's Mutual Defense Assistance Program and received military aid.
"Stop sending people to kill me. We've already captured five of them, one of them with a bomb and another with a rifle. [...] If you don't stop sending killers, I'll send one to Moscow, and I won't have to send a second."