I had started a new game with "Update Construction Drones" mod, version 2.0.4, and started playing through the game. At some point when when creating a spaceship, the game crashed, and said the mod had triggered an unrecoverable error.
I disabled the mod and kept playing.
The next time I use a nuclear missile, I got the "I am the destroyer of worlds" achievement in steam.
My memory is fuzzy, but I could have sworn that once a save game is modded, it stays marked as modded and you can never get steam achievements.
[2.0.47] Got a steam achievement on a (previously) modded savegame
Re: [2.0.47] Got a steam achievement on a (previously) modded savegame
Thanks for the report, this is not a bug. We don't prevent modded saves from getting achievements if mods are later removed.