Here is the full list of all 12 FEZ achievements. It takes around 10-12 hours to unlock all of the achievements on Windows.
Find ALL collectibles.
Collect all 32 Golden Cubes and 32 Anti-Cubes.
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Find the Skull artifact.
Get to the end.
Find the Tome artifact.
Break the code.
Find your very first cube shard.
Find the Writing Cube artifact.
Find the Counting Cube artifact.
Find an Anti-Cube.
Reactivate all 5 warp gates.