Here is the full list of all 15 Boggle achievements worth 1,000 gamerscore. It takes around 40-50 hours to unlock all of the achievements on Xbox One.
You' played 500 online games.
You played 500 classic games.
You finished first in an online game 100 times.
You found 3000 3-letter words.
You found 80 words of 8 letters or more!
You found 210 7-letter words.
You found 1500 5-letter words.
You found 2400 4-letter words.
You finished first in an online game.
You found 600 6-letter words.
You reached the Diamond league. Congratulations!
You are part of the Elite.
You found all possible words on a grid.
You scored more than the maximum points possible. MAGIC!
You can do no wrong (20 correct words in a row).