Here is the full list of all 20 The Jackbox Party Pack 3 achievements. It takes around 6-8 hours to unlock all of the achievements on Windows.
Pick top three answers in final round
Write "gravy castle" and win a battle with it
Create a custom game
Faker gets through three tasks in a row without a single vote (or two tasks for three player games).
Answer 5 Trivia Questions in a row correctly
Play 3 games in a row with the same players
Win all your battles in Round 1, but lose all your battles in Round 2
Get a Super Quiplash! (all player votes and 90% audience votes in a 5+ player game)
Survive The Killing Floor 3 times in one game
Get all the votes in a single battle in a 5+ player game
Vote against your own shirt in a battle
Use all of your colors in a single drawing that then gets used on a shirt
Catch the Faker on the first vote.
Be the creator of every shirt in the final gauntlet
Play five games of Fakin' It in a row.
Play 40 You Gotta Point tasks.
Get a score of 25 or more in the Math Killing Floor
Guess the exact percentage
Perfect guessing of higher/lower
Guess within 5% of an audience's answer