Full list of all 11 Who Wants to be a Millionaire? achievements worth 1,000 gamerscore.
Achievements they've won
Achievements they've not won
Answer 10 questions correctly at the very last second on the timer.
Answer more than 1000 questions correctly
Become the champion in cooperative mode.
Answer more than 500 questions correctly
Become the champion in normal mode without using a lifeline
Become the champion in normal mode
Answer more than 100 questions correctly
Rack up 150 seconds on the timer.
Become the champion in easy mode
Reach question 10 in normal mode
Reach question 5 in normal mode