Microsoft Ultimate Word Games

To obtain three stars on a crossword puzzle, you simply have to complete it. Considering the amount of crossword puzzles you'll have to finish to reach level 80, you should definitely unlock this naturally. This is most easily done on the first 15 crossword puzzles of adventure maps from July 2017 onward. The first 15 puzzles of these maps are only 10x10 grids instead of the standard 15x15, and not only are they smaller but they are incredibly easy. Keep in mind for this achievement that even though you can't use hints, you can Google answers, use a thesaurus, and use "check puzzle" to see if you have any wrong answers as many times as you want, just so long as you don't use a single hint to finish the puzzle.

The achievement will unlock upon getting the third star.