Easy Race achievements - Set the fill to 15 lines and clear 40 lines in under two minutes.

Easy Ultra achievements - Keep the time at one minute and increase the level to 15. Get at least two Tetris or close to it.

Accomplish the indicated achievement to get the corresponding number of Gamerscore points:

Marathon Tin Medal (5 points): Get 100,000 points playing Marathon.
Marathon Bronze Medal (10 points): Get 200,000 points playing Marathon.
Cascade Bronze Medal (10 points): Score 100,000 points playing Cascade.
Ultra Bronze Medal (10 points): Score 5,000 points playing 1 minute Ultra.
Race Bronze Medal (10 points): Clear 40 lines in under 4:00 playing Race (Single Player).
Score Bronze Medal (10 points): Get 25,000 points in under 10:00 playing Score (Single Player).
Hotline Bronze Medal (10 points): Get 25,000 points playing Hotline.
Eraser Bronze Medal (10 points): Clear eight target lines in under 1:30 playing Eraser (Single Player).
Go Low Bronze Medal (10 points): Get 30,000 points playing Go Low.
Back to Back (15 points): Do two Tetrises or T-Spins (Single or Double) without clearing any lines in between in Marathon.
Rollin On Spinnas (15 points): Pulled off the infamous T-Spin playing Marathon.
Marathon Silver Medal (15 points): Get 250,000 points playing Marathon.
Cascade Silver Medal (15 points): Score 200,000 points playing Cascade.
Ultra Silver Medal (15 points): Score 12,500 points playing 1 minute Ultra.
Race Silver Medal (15 points): Clear 40 lines in under 3:00 playing Race (Single Player).
Score Silver Medal (15 points): Got 25,000 points in under 7:30 playing Score (Single Player).
Hotline Silver Medal (15 points): Got 50,000 points playing Hotline.
Eraser Silver Medal (15 points): Clear eight target lines in under 1:15 playing Eraser (Single Player).
Go Low Silver Medal (15 points): Get 40,000 points playing Go Low.
Give Em Twenty (20 points): Send 20 lines in a Xbox Live game.
Back to Back and Back Again (25 points): Do three Tetrises or T-Spins (Single or Double) in a row (Back to Back to Back) playing Marathon.
Marathon Gold Medal (25 points): Get 350,000 points playing Marathon.
Cascade Gold Medal (25 points): Score 300,000 points playing Cascade.
Ultra Gold Medal (25 points): Score 25,000 points playing 1 minute Ultra.
Race Gold Medal (25 points): Clear 40 lines in under 2:00 playing Race (Single Player).
Score Gold Medal (25 points): Get 25,000 points in under 4:00 playing Score (Single Player).
Hotline Gold Medal (25 points): Got 100,000 points playing Hotline.
Eraser Gold Medal (25 points): Clear eight target lines in under 1:00 playing Eraser (Single Player).
Go Low Gold Medal (25 points): Get 50,000 points playing Go Low.
Live Playa (30 points): Win an Xbox Live game.
T-Spin Deluxe (30 points): Pull off a T-Spin 2-Line Clear playing Marathon.
Ludicrous speed (30 points): Clear a line on Level 15.
All about the Hamiltons (30 points): Score 100,000 points with Fill Rate set to High in Cascade.
Take it Off the Top (50 points): Clear line 20 of the Matrix.
Big Ol Cascade (50 points): Trigger 8 or more Cascade Line Clears with a single drop.
A For Effort (50 points): Play 100 games (Single Player).
Old Skool Back to Back (50 points): Score 2 Tetrises in 2 drops playing Marathon.
Went Low (50 points): Clear the Matrix completely playing Go Low.
Dirty South Style Back to Back (75 points): Score 3 Tetrises in 3 drops playing Marathon.
Marathon Platinum Medal (75 points): Get 500,000 points on Marathon.