You're still new to Tekken, but you kind of understand frame data a bit. Then you hear some folks mention that certain moves are 'unsafe' or 'launch punishable'. What's that all about then?
You already know that when you block someone's move, you get to do stuff before them. Well, for some blocked moves that amount of time is so large that you can hit the opponent with a guaranteed move of your own before they can recover and block.
This is called punishing, and moves that can be punished are called unsafe.
Unsafe moves usually have great rewards when they hit, so if you can't punish such moves properly the risk-reward is very much in your opponent's favor.
Because this write-up turned out kinda super long again, here's the TLDR for folks who aren't about that:
If you block big dangerous moves (such as launchers), make sure you try to hit the opponent with a pretty fast move afterward and remember if it worked or not.
If something worked, try to hit it every time you block that move. Don't let folks get away with unsafe shit.
Anyway learning to punish well in Tekken takes time, and it's something you pretty much will be improving on forever. But don't let that put you off, you can just start with the common stuff and add more things as needed. Even the best players in the world don't always punish perfectly, so it's not expected that you would.
Punishing a move properly is essentially a three step process:
1. Recognizing the move you just blocked
2. Knowing what your character's best punish is for it
3. Executing that punish
Recognizing the move you just blocked is pretty tough. Tekken has a lot of characters and each of them has a gigantic movelist. Your best bet is to focus on the essentials, the punishable tools each character uses the most. On top of that, many characters share certain basic design choices. Most hopkicks look similar and most of them are around -13 on block. Most power lows stagger on block, giving you time to do your strongest punish.
You don't need to know the specifics in these situations, just "Oh, that looks like a hopkick, guess it's time for the 13 frame punish".
Also it just comes with experience. I recommend getting into a habit of looking up the details of a certain move right after it gave you trouble in a match, one move at a time. It's manageable and gives you the feeling of looking for a productive answer to a recent problem, which is nice.
Knowing what your character's best punish is for a move is also kinda tough. In essence you have to know your punish for every punishable move in game-- wait, don't run away in terror yet! There are ways to structure this and pare it down to the essentials.
The best and most reliable way to determine a punish for a move is to just go into practice mode, record the dummy to do the move and then block after, and then -you- block the move and try your punishes.
Since this takes time, sometimes it can be faster to just look at frame data to see how negative a move is.
You have to be careful though. Some moves can be less punishable at longer ranges, or spacing can make the move you have at that speed simply not reach. Leo's d/f+2 above is a good example of both. Up close it is -13, so you have time to hit her for free with any of your moves that are 13 frames or faster. At longer ranges it is only -12 and most 12 frame moves just don't reach that far, so it becomes safe in this way.
By contrast, her d/b+4 is -31 and she's locked into this huge stagger when you block it. 31 frames is enough for you to do basically any move you have and it will connect before she can block. Since it is a low, you'd be crouching when you block it so throw out the most powerful launcher you can do from crouching.
In any case if you want to know what punishers you have, going through the whole movelist and trying all the things would be an insane work burden. Luckily Tekken has some universal structure applied to its frame data, so it's advised to learn that and then take note of any applicable exceptions.
So, remember this:
When you block a move that is 0 to -9 frames on block, most characters can't do anything so that move is safe. You still have advantage of course, so use it to pressure them.
When you block a move that is -10, most characters get a jab punish for small but relevant damage and good advantage after, so moves of this caliber or worse are unsafe.
When it's -12 or -13, characters start to get punishes for significant damage and/or knockdown.
At -14, characters get mini-launches or strong hits into knockdown.
At -15 or more, most characters get a launch into a full combo so these moves are called launch punishable.
So, how do you find your character's punishes for those numbers? Either you spend a lot of time in training mode to try all the things, or you ask more experienced players of your character. Either in person or online. Communities like Tekkenzaibatsu, tekken reddit or the tekken players on neogaf or wherever can help you. There's also various FGC discords or twitter or youtube. Look around. Find folks to connect with. Doing everything on your own is inefficient and kinda awful.
So lastly, executing your punish properly is just practice. Hop to it! Tekken has a pretty generous input buffer so anyone can learn to get the proper timing down with some practice. And if you mess up, don't worry. Everyone messes up at some point. Play it safe if you're not sure if you can do it, getting a weak punish but ending at advantage is sooooooo much better than failing at the perfect punish and eating a bunch of damage yourself.
Well, that ends this three part series on frame data (and punishing). Congratulations and thank you for sticking with it for this long if you've managed to get this far. I hope you learned something, even if just a little bit.
But in the end these are all just words and the main thing is always to play more. Play and have fun.
Also feel free to contact me for some matches or if you'd like to see more words about a specific Tekken subject or you have trouble with something.