Kerala: As you mention, not a country. Also didn't really seize the means of production. But when I think of Communism working well, it's at a local level like this rather than at the level of a country. There are communes and kibbutzes that lasted decades. Generally a tough life but at a small level you can have a government controlling everything without hopefully making as many huge mistakes. Worst case you can more easily just leave if they do (hopefully they let you).
Chile: Also didn't fully seize the means of production, it's more or less a perfect example of a government that's run by a socialist majority for a small amout of time and which enacts socialist measures during that time, but never reaching full communism. This is the kind of thing I would hold up as the ideal case. Socialism for long enough to strengthen the situation of the people, but not long enough to wreck the economy and grow into full blown authoritarianism.