For this you’ll need to complete Marathon and every variant on level 15 (apart from Radical). Marathon, the first variant (which is a short marathon) and gravity are the easiest and don’t require anything in particular. Be sure to use your hold function as it’s extremely useful.
Treadmill is like normal except that with every Tetrominos you place the bottom moves, it’s a bit confusing at first but then you get the hang of it and it even makes the game easier.
Gravity means that if ever you would have had a floating single piece, it now falls. This is essential for Cascades. If you play smart you won’t ever need the Gravity function.
Flood is when the matrix fills from the bottom. This is the first tricky one. Quickly dispatch every line as fast as you can as it can get out of hand very fast. As far as I can tell the holes in the flood lines are random.
Ledges is pretty straightforward and there isn’t much to say.
Laser is where it starts to get tricky, really the only tip is the same as for the other variants, be as quick as you can and don’t try to get novelty moves.
Magnetic is pretty straightforward, although you’ll find yourself cursing yourself over how dumb you are.
Scanner is pretty straightforward and not too complicated although things can get out of hand fast if you’re not quick. You can try to get the Dodecadent achievement here although it’s pretty tricky; to do so hold an I-shaped object and stack as many lines as you can, leaving either on the far right or on the far left enough room (and just enough room) to fit three Is one on top of the other and when the scan goes you should have cleared 12 lines. This is the method to finish games with only Tetrises, it’s sort of tricky at first but once you’re used to it it’s a breeze.
Split isn’t that bad, the matrix is separated in two and you have to keep clearing lines. It’s absolutely essential that you use the hold function here.
Chill is where it starts to get really hard. You have three placements before the objects start to freeze into place. There are three stages to freezing: blue (which isn’t frozen), light blue and gray. You can clear a line with blue and light blue objects but gray will stay in place until their line is cleared which makes them turn light blue. You basically have to take them down twice. This gets kind of annoying as they’ll get stuck in weird places sometimes. It’s from this point on where you probably won’t get complete the variants on your first try on level 15.
Flashlight is sort of hard. It helps to have a photographic memory. When you clear a line the matrix will light up which helps immensely.
Best for last, Radical variant. By far the hardest one although to be honest, they could have done it a lot harder (by mixing in some elements from other variants for instance). Be quick and sneak your way around by turning the Tetrominos. I got this on my third try I think; it’s hard but not impossible.
That should net you the 100%.