Cammy is a bitch but that’s if you respect her too much. What you want to do is zone her out and figuring out how she wants to get close to you; a safe Spiral Arrow or Razor’s Edge Slicer loses to SJ lk BK, you should be able to react to a max range Quick Spin Knuckle with lp TK or a hp TK if closer. Once you get her to try walking towards you, you want to play the footsie zoning tactics like instant air mk burning kick, f.mp if they like to try and dive in on you and also the standard c.mk xx shenanigans once you condition them to stay grounded and be wary of s.mk and s.hk (try to focus this one) if you get close to her work out if they are going to respect you or not, if they don’t respect you bait that shit and make them respect you, if they already respect you then go to town like they do on you.
If you’re on the blocking end just try to use lk BK to get out if they’re doing tight strings, if they are hitting you out of it then just do hp tk where you’d normally be able to do lk BK. If they try to block either one then just mash back dash if you’re not in the corner or SJ out if you are in the corner, also learning how they set-up the cross up dive kick and learning which side they land after a dive kick is very important as well. I haven’t tested it yet but you should be able to force out their OS by doing hp TK feint on wake-up too.
Guy is definitely one of her harder match-ups, in dealing with the elbow you must learn to reaction s.mk the close one and if they’re baiting you once you start doing that, they generally will be OSing the punish for the bait so try to punish the OS instead of the elbow, which is generally the slide so when zoning him and you see the elbow drop do SJ lk BK or f.mp, if they’re not OSing then just do the standard c.mk on landing. Footsie wise he’s much harder than Cammy because of s.mp post special move, that move will fuck with pretty much everything unless you have EX Seismo stocked, if you do just run the standard c.mp xx mp tk > ex seismo bs until he stops when you have meter and if he uses slide to counter that then just do f.mp to counter his counter. If he does stop at max range SJ lk BK and hits out his slide.
On wake-up just watch and see what he does, EX Spin Kicks beat out cross-up BK stuff clean while EX Run gets him out, if he does EX Run on Wake-up then just time your hp TK the standard s.lk timing to block EX Spin Kicks and still hit him out of EX Run, when he has no meter is the only time you can do the cross bk shenanigans on his wake up. If he gets you to block then you don’t really have an option outside of taking a risk and trying to escape and EX Seismo gets hit out of 90% of the time and all his moves are safe including slide at max-ranges so yeah, just another match where you have to go on the offensive before he does.
Hardest Match-Ups IMO are:
Rufus
Guy
Adon
Yun
Yang
Against proficient users (Tough):
Ken
Cammy
Dee Jay (That’s right Dee Jay)
Juri
Makoto
Vega
Rose
Zangief
With enough knowledge and experience not really that tough just annoying:
Bison
Honda
Balrog
Fei Long
El Fuerte
Basically the 1st and 3rd category don’t allow Viper to play the way she wants to that’s all whifch is why they are so hard because it’s so unnatural to restrain her playstyle, the 2nd one has options to shut her down if they know what to do so you have to play smartly to win.