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Blanka
Cammy
Chun-Li
Dee Jay
Dhalsim
E.Honda
Guile
Jamie
JP
Juri
Ken
Kimberly
Lily
Luke
Manon
Marisa
Ryu

Playing against Ryu is generally about staying patient and punishing his overextensions or predictable moves. His toolset is well-rounded enough that rushing him down can be dangerous without establishing enough of a presence to make him afraid of using his best tools for punishing overzealous players, and Cammy has a less difficult time giving Ryu trouble for pushing his offensive too hard. Against a Ryu that likes to throw a lot of fireballs, parrying them from farther out is the safest option, followed by neutral jumping over them; forward jumps are much riskier, as Ryu can and will DP you out of the air if you get the jump approach wrong. The riskiest but subsequently more rewarding option is MP/HP/OD Spin Knuckle if you have a strong read on when the fireball is going to come out; timing it correctly will give you a counterhit and skip you right through the fireball. Note that experienced Ryu players will often bait Spin Knuckle by shuffling at roughly fireball range and occasionally neutral jumping or going for a Drive Impact if they anticipate it coming, so be careful about using it too much; in the case of a Drive Impact, it's possible to get through the fireball and potentially (but not always) recover in time to counter-DI by using MP Spin Knuckle instead of HP or OD. If you happen to have 3 super meters and really trust your reactions, then a careless fireball can also be shut down by SA3 or Critical Art, though it's best to save this for when a kill is assured.
Aside from that, it's best to use Cammy's medium kicks and 5HK when trying to feel out the neutral, or go for whiff punishing buttons like 5HP if Ryu whiffs one of his slower buttons. Unlike a lot of other characters, Cammy can pretty easily punish Ryu's sweep if it's blocked, either with 2MK or a Spiral Arrow if the distance is a concern, and while Ryu can space High Blade Kick to be safe, a 2MK will punish the LK, MK, and OD versions pretty easily if you're unsure of the range. Make good use of shimmying after getting knockdowns with Spiral Arrow in order to bait Shoryuken, and keep an eye out for Drive Rush normals -- the most common picks that a lot of Ryu players like to use are Drive Rush 2MK and Drive Rush 6MP.Zangief

In a general sense, you do not want to overcommit to fighting Zangief up close. Spend a lot of time walking back and forth poking him where you can, ideally with 2MK and 5HK, though be careful with being too overzealous with your longer reaching buttons as he can grab any extended throw hurtboxes with Spinning Piledriver. If you can get a hit that converts into a Spiral Arrow, take the knockdown as an opportunity to get closer and go for jabs or meaties, but if he blocks, be willing to back off. If his Cyclone Wheel Kick overhead (6HK) isn't spaced correctly in neutral, it can be punished on block with the likes of 2MP, 2HP, or 5HP, and you can get a knockdown from whatever combo that follows. If you do get hit by Spinning Piledriver, Siberian Express, or other throws that create significant distance between you and him, you'll need to gauge your next actions relatively carefully if he chooses to Drive Rush at you -- while Drive Impact will shut down most of the Drive Rush normals or command normals that Zangief is likely to use after a Drive Rush, Drive Rush Knee Hammer (6MK) can be made just safe enough for him to counter-DI in certain circumstances, and while neutral jumping is an option if he's far enough away, you may also get snagged by his SA1 or OD Siberian Blizzard (air Spinning Piledriver) if you do this too often. If he chooses to throw you with his other unique normal throws that leave him much closer to you, you may have to gamble on challenging with OD Cannon Spike to deal with grounded oki.
If Zangief begins to jump at you to get in, use Cannon Spike or air-to-air normals to knock him out of the air and keep him from using his buttons to cover his approach; of the two, Cannon Spike generally works best since it has air invulnerability on its startup frames, which will keep some of Zangief's beefier normals from counterhitting your air normals. Cannon Spike also works as an answer to Knee Hammer if he's using it on the ground to advance a lot, as it's oftentimes a tool Zangief players use to buffer a Spinning Piledriver input when they land from it and he is in the air for a period of time while using it. Be especially wary against a Zangief that seems to jump or otherwise move more aggressively when he has 3 super meters, because it's likely that they're fishing for his SA3 or Critical Art if they can get in range for it. The only way to avoid it is to be out of range or otherwise not throwable before the super flash goes off (unlike Lily and Manon's SA3s), or you're caught. Once he has the meter for SA3/CA, you should be even more proactive in avoiding a close-range fight with him, which extends to changing too -- Zangief's SA3 is somewhere between his LP and MP SPD's range, slightly cutting back on its range compared to the Critical Art version, which is within LP SPD's larger range. This may mean committing to more neutral jumps or backdashes after knockdowns if you suspect that SA3/CA is going to come out.