Adding to this a bit.
Off a regular jump in or FADC (as close as possible, basically):
s.MP, TC2 xx HK Gekiro: Cammy, Cody, Dudley, Guy, Hakan, Juri, Makoto, Sagat, Seth, T.Hawk, Zangief
s.MP, s.HP xx HK Gekiro: Adon, Akuma, Bison, Blanka, Dan, Dhalsim, Evil Ryu, Fei Long, Gouken, Honda, Ken, Oni, Rufus, Ryu
s.HP xx HK Gekiro: Abel, Balrog, Chun-Li, C.Viper, Dee Jay, El Fuerte, Gen, Guile, Ibuki, Rose, Sakura, Vega, Yang, Yun
So one way or another, it works against the entire cast. You aren’t even sacrificing damage really against anyone but the last group. You can usually use s.HP xx HK Gekiro in situations where you’d use TC2 xx LK Gekiro, like punishing a shoto DP. It should be reliable against all the characters in the second group, and many in the third. Guile, Dee Jay and El Fuerte are characters where you should almost never try it, unless it’s off a jump in or FADC combo.
Edit: Off a focus crumple, a few characters get moved from the two-hit group down to the one-hit group, and I underlined them. Also, it’s generally better to delay your attack until the other character falls on their knees, so you get a little closer.
Off a crossup:
TC2 xx HK Gekiro works against the same characters as the first combo above, against some you can even include the s.MP but it’s finicky.
s.HP xx HK Gekiro works against everyone else EXCEPT: El Fuerte, Fei Long, Gen, Guile, Ibuki, Rose, Sakura, Vega, Yang, Yun
It may actually work against some of them if you hit the crossup just right, but it’s unreliable.
Now, setups off the untechable knockdown.
An easy but complicated safe jump setup I’m using is:
- Hold up forward in Crane, whiff an attack in the air, stance change during your landing frames, neutral jump in Mantis.
You actually need to get the 5 frame stance change animation on the ground to help delay it. You usually want to finish with the opponent’s head level slightly above Gen’s, but characters that have slower wakeups may need to be even or lower. It can be adjusted to work against everyone that can be safe jumped. It works well at midscreen or all the way in the corner (neutral jumping in Crane) but I could really use an alternative setup for when jumping forward would put me in the corner.
Crossup wall dives are more complicated, you need different setups depending on whether you did a close range combo/punish or a combo at the edge of your range. It’s probably the best setup in the game though, considering the control you have over the spacing and the time to adjust. There’s enough time to whiff hands just to build meter before doing a wall dive.