A massive change they made to the achievements in TE:C for Steam is the fact that Seriously? Seriously. no longer requires SS ranks everywhere. That being said, you still need at least 10 for Super Savvy. SS Rank Requirements are given first, with S Rank just below that for this guide.

Marathon: Score 500,000 Points and complete the Marathon
S Rank Requirement: 400,000 Points

Tips:

• It should go without saying, but chain your Tetrises and T-Spins to rack up your score. The target score is fairly high for this one!
  
• If you're confident, or your score still isn't reaching the required number, you might want to up the starting Level. This will make the earlier lines you get score more!
  
• Alternatively, if you have a lot of time on your hands, you can just play Endless Marathon and just see how high you can get your score before topping out.

Zone Marathon: Score 1,000,000 Points and complete the Marathon
S Rank Requirement: 800,000 Points

Tips:

• Since this is an Effect Mode added after launch in an update, this one is not a requirement for "Seriously? Seriously."
  
• Every 8 lines cleared grants one quarter of your Zone meter; this also applies to Journey Mode (on Normal and Expert).
  
• If you want any shot at getting this score, you've got to use your Zone as often as possible. The ideal method is to use Zone and immediately clear 8 lines (2 Tetrises' worth) or more within the 5-second window. Doing this will give you a better shot at the necessary 1 million points needed.
  
• Lines cleared in Zone don't increase the line clear count to complete the Marathon, but they will increase the rate at which the game will speed up. Watch out!

Ultra: Score 35,000 Points
S Rank Requirement: 30,000 Points

Tips:

• This one can be tricky due to the time limit. Back-to-Backs of T-Spin Doubles and Tetrises should be enough, but you need to work quickly.
  
• If you can get an All Clear or two, this one will be that much easier. Keep practicing on this one!

Sprint: Time of under 70 seconds (1:10).
S Rank Requirement: Time of under 80 seconds (1:20)

The only tip I can give for this one is to keep practicing. This one is a pretty big pain if you're not used to playing fast. You need 10 Tetrises in 70 seconds (80 for S rank); practice this one along with Ultra and see how well you can do!

Master: Clear 150 Lines.
S Rank Requirement: Clear 130 Lines.

Tips:

• If you're not used to playing at 20G, then this one can take a very long time to complete. Blocks drop straight to the bottom of your matrix, and as the levels go higher, the time before tetrominos lock and line clear delay both drop, making each level faster and faster.
  
• There aren't a lot of instances where 20G is in effect elsewhere in the game. The only place where 20G even occurs is at very high levels in Connected Score Attack and Expert Journey Mode, where some stages have places where it hits Level 20, which is 20G. If you want to practice before taking this on, try one of those two area.
  
• The Connected Zodiac Boss Scorpio also has the Fast blitz, which temporarily increases the speed, and late in the game emulates Master-level speeds for a short bit.
  
• Because Score doesn't matter, you should always start at M1. Good luck!

Classic Score Attack: Score 250,000 Points
S Rank Requirement: Score 200,000 Points

• Since this is an Effect Mode added after launch and in an update, this one is not a requirement for "Seriously? Seriously."
  
• The rules in this mode are drastically different from Standard Tetris we all know and love. I highly recommend watching some Classic World Tetris Championship (CTWC) to see how it works. The fundamentals are very different, including No Hold, 1-Piece Preview, No Hard Drop, complete piece randomization, and a fast lock after the tetriminos hit the bottom.
  
• I want to quickly bring up the randomization thing real fast. The pieces you get are completely random; it doesn't use the 7-bag randomizer that's commonplace in Tetris today. Modern Tetris randomizes the order of the seven types of tetriminos, sends them in that order, so on and so forth. This means the maximum gap between I-pieces is 12 - assuming it rolls first in a bag and then last in the very next one. This makes pieces fairly consistent without it being unfair. Classic Score Attack does not have that; you have an equal chance of getting any of the seven pieces next. This means you can go for long "droughts" of not getting an I-piece for Tetrises. Be careful!
  
• Back-to-Back and Combos do not exist in this mode. There is no bonus for clearing Tetrises back-to-back or combos.
  
• You'll likely need to crank up the initial level speed to get a better score.

A general tip for each of these: Don't top out. While topping out doesn't result in a Game Over, it does reset your score to 0.

Chill Marathon: Score 300,000 Points
S Rank Requirement: Score 200,000 Points

All Marathon tips apply here, but requires a significantly lower score. Just avoid topping out, and this one won't be too much trouble.

Quickplay: Score 10,000 Points
S Rank Requirement: Score 8,000 Points

Just chain Tetrises here and you'll get 10,000 easily. This is also a decent place to practice for Sprint; you'll get 8 of 10 Tetrises for a Sprint time if you do 30 lines!

The required score for these ranks is calculated per 30 lines and level. As an example, Level 5 for 150 Lines will require 250,000 Points, 25 times more than normal!

Whenever Relax is the Weekly Ritual, this is easily the fastest one, able to be done in around a minute for an SS rank. This is a great one to grind for Avatars on to progress for Avatar Rockstar, where you need to collect 100 unique avatars! Three will unlock at every multiple of 10 (except 50).

Ambient / Playlist: Score 40,000 Points
S Rank Requirement: Score 32,000 Points

Nothing complicated, just get through the four stages with a decent score. Just make sure your board is in decent shape between area transitions.

All Clear: Get 30 All Clears
S Rank Requirement: Get 26 All Clears

Tips:

• Memorize the patterns you get! They'll keep showing up if you keep playing.
  
• The first 20 or so shouldn't be anything too complicated; try not to mess these up.
  
• Memorize how to spin those S and Z pieces into place, along with the T-Spin setups. Knowing how to get these setups will make this challenge much, much easier.
  
• You still need to move pretty fast on this one; you don't get a lot of time refunded for getting the All Clears, only about 3-5 seconds!

Combo: Make 120 Combos
S Rank Requirement: Make 100 Combos

Tips:

• This one is more about speed than you might think. 120 (100 for S Rank) is a lot, but for each combo you get a small amount of time back; move quickly!
  
• Don't be afraid to "dump" a few pieces if a combo won't start with the pieces you have at the moment. Put them at the top and out of the way of the combo.
  
• The Combo doesn't start until you clear a line, which is why you are allowed to pass on pieces that are not ideal.
  
• The time refunded gets smaller as the timer closes on 0. Try and keep up!

Target: Clear 30 Boards
S Rank Requirement: Clear 26 Boards

Tips:

• You're going to want to get creative for this one. You only need to clear the glowing blocks; every other one can be ignored.
  
• Stack high enough so you can clear the blocks required. Later boards will have blocks above the one you need to clear, requiring you to clear those lines. Those should be the only ones you clear that don't contain the target blocks.
  
• You gain a decent amount of time for clearing boards, but a target of 30 (26 for S rank) is still pretty far out there. Try to be efficient and quick.

When Focus is the Weekly Ritual, do whatever one you can consistently get an SS on. For me, that's Target. Find the one you're best at and keep at it!

Countdown: Score 55,000 Points
S Rank Requirement: Score 42,000 Points

Tips:

• Lines cleared by the dropped I-pieces score double! Use them to your advantage to rack up your score.
  
• That being said, mind where they drop and make sure they don't make your board worse than before!
  
• You have 5 minutes to get the needed score. If you're struggling, this mode has an Endless mode for you to get the SS Rank; you only need it for one of the two modes.

Purify: Clear 450 Dark Blocks
S Rank Requirement: Clear 400 Dark Blocks

Tips:

• If you play competitive Tetris, then your downstacking prowess will serve you well here. High combos will cleanse many Dark Blocks at once, far more effectively than even a Tetris!
  
• Cleansing all Dark Blocks will give you some bonus points. Make an effort to cleanse them all before more blocks get infected!
  
• You can also cleanse blocks by simply clearing them. Worth knowing if your board gets low.
  
• There's also an Easy mode and Expert mode available, along with an Endless.
  
• This is the best one to do for Adventurous Weekly Rituals due to the short 3-minute time limit.

Mystery: Score 400,000 Points and complete the Marathon
S Rank Requirement: Score 300,000 Points

Tips:

• Like Marathon and Countdown, there's an Endless mode for this one. If you can survive long enough, it's something to consider to get your SS for this one.
  
• There's a secret zone which doubles your points. If you get it, take advantage of it.
  
• The next effect takes place after at least 10 Tetrominoes have dropped; you'll notice a sound cue and the background darkening, along with a purple glow to the matrix. Pay attention and try to anticipate the effects!
  
• If you get a Bonus Rally, maximize your points for those few pieces you get, because it won't last long. Likewise, if your speed resets, take a breather and don't misdrop any pieces. Get an All Clear? Count your lucky stars, because that also awards points!
  
• Unfortunately, you're at the hands of the game for this one. There's always a chance you can go a full run without seeing a single beneficial effect, which can help immensely. Good luck!