Thief

The Theif achievement is awarded for stealing 50 crates of spice from any other sentient species. This must occur over the course of one save file.

Tips and Tricks
Rather than steal an empire's resources and risk going to war with them, it is easier to find a planet with a civilization on it instead and steal their spice. Since home planets usually have 5-10 cities on them, by the time you have stolen a spice crate from every city, you can return to the first one you stole from and it will have another spice crate for you to steal. By repeatedly circling a planet like this, you can earn theif rather quickly and have a lot of spice, as well. In fact, since this approach requires no additional spaceship tools, you can do this early in the game even if you already have the achievement and it will yeild enough spice to get you several iterations of the Golden Touch badge.

WARNING! if you spend too long on a civilized planet, one nation may eventually capture every city. This will cause them to advance to the space stage and go to war with you for your exploitation of them.