"Alright, this time we'll try the exploding cigars! Put the LSD spray on hold!"

Explanation: After the split between the (capitalist) US and (Soviet-aligned Communist) Cuban governments became decisive in the early 1960s, the then-fairly-new CIA decided that Cuban revolutionary leader Fidel Castro’s popularity and high level of influence meant that killing him would substantially destabilize the Cuban government’s hold on power (not an unfair analysis, if an amoral one).

The Cold War being what it was, the CIA spent the next ~30 years, at least, attempting all sorts of wild fucking assassination plots, from packing sea critters with explosives, to fungal infestations in his clothes, to just bribing his lover to poison him.

None of them worked. Castro would die of natural causes in 2016, at the age of 90, still in a position of immense political influence in Cuba.