All these things are opinions at this point, but a couple of top players have this opinion at this point:
1. He is legitimately hard to zone. With slide in one variation and his deep freeze in another and a ridiculously fast dash in both, it makes it so he will more often than not have the edge against traditional space control.
2. His B1 is -2 on block. Add this in with the fact that his backdash is incredible and this is crazy. He could poke then backdash to bait a counterattack and it could be used as a check for the opponent to be hesitant to press buttons in neutral.
3. 12 is 0 on block. The same thing with B1, but better. After this is blocked he could backdash and whiff punish pokes but he could also just tiny dash forward and grab the opponent. This again creates a fear for the opponent not to want to press buttons just opens up his crazy mixup game of low-grab-overhead.
4. He's going to have a TON of grab opportunities. Unlike many, he actually has an overhead low mixup. It doesn't matter if the overhead is punishable because it's practically unreactable and what is more important is the fear that it even exists. Not many will often take the risk to preemptively D2 or neutral duck without blocking to punish a grab attempt.
It's easy to think that Subzero has to be played risky with just doing overheads and lows, but if someone just focuses on dash-up grabs and footsies, this character ends up doing that slightly better than some that specialize in it. Dash-up ANYTHING is just really really fast.
As far as the "worst" characters these are just my personal opinions.
The whole thing is some characters just execute strategies a little better. Raiden and Kotal are still very much useable and will end up having some winning matchups with their tools. They are actually really solid characters still tbh. I just predict they might have more losing matchups than a few other characters.
The reason I said Raiden is because he has to commit completely to his offense. What I mean by that is that most of his tools in neutral leave him in a position where he has to commit to a block afterward because he is barely safe on block. Once he commits to his normals, his turn is over and the opponent could do what they want.
Raiden has some good space control projectile zoning in one variation and if he could optimize this game in some matchups he'll do fantastic. In his other variation he has to focus a bit more on his normals and the only way to truly make it so you get away free when using his stuff is by using a defensive bar to cancel his tackle (and he needs that bar). If played great, I don't doubt Raiden could be a beast who hits like a truck and could even mix you up if he's close enough though.
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Kotal has an amazing real stagger with F34. The recovery on F3 is the same as the startup for the F3(4) second hit, so the opponent literally has to guess if he is going to complete the string or not. That AND he has a command grab mixup in F3xxGrab. If he does commit to the F34 he is -3 which is really not too bad either. He also has F12 which is an incredible neutral tool that could lead into a full combo too and is safe on block aswell.
All this stuff is really good. Combine it with his dash speed and he is going to be a serious threat. The thing is that he has one big flaw and that he really does have to play the opponent's game completely if he is up against a character that could run away from him properly. He could switch to his variation with the jaguar moves, but he'd lose a ton of the utility from his combo extender and his command grab. In some matchups I predict he might have to take some big risks just to get in and do a F3 mixup.
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Like I said before though, both of these characters are good. They have gameplans that work and will definitely have some winning matchups. Like I mentioned though, I just predict they might end up having a bit more losing matchups than some other characters because their gameplans are so all-or-nothing imo.
And about Sonya? She could make her mix safe with rings. Her rings are themselves a mixup because she could cancel her amplify to continue pressure and the opponent has to be afraid of that absolutely crazy ring krushing blow. Her projectile is incredible just on its own so she could keep some people out until she wants to dash in with a mixup. Her damage is very high for how many tools she has too. I just feel like she doesn't really struggle against anything.
