Update: As per ph00tbag's post below, near the start of a combo, using 2C > 5C nets slightly higher damage than using 5C > 2C.
Here's a dump of my current best combo options:
First off, this one was based on Silk's. It adds 300 damage (2.27k), but it doesn't quite build the 1 magic by the time you need it, so you DO have to have at least a bit of a bar before you land it.
2a > 2b > 2c > 623a > 5c > 2c > 3c > j.a > j.b > 6a > 5c > 2c > 3c > 1d > 236b > 6a > 5c > 214c > dash > 5c > 214b > super
My go-to BnB if I've got a bit of magic to burn, especially good when your best punish is 2B. Also works fine if you start it with 2a > 2b > 2c > 623a, just loses like 200 damage. (3 magic, 1 super, 2.79k).
2b > 5c > 2c > 623a > 5c > 2c > 3c > 1d > 236c > 5c > 2c > 1d > 5c > 2c > 3c > 1d > 236b > 6a > 5c > 214c > dash > 5c > 214b > super
A zero-magic corner loop. I don't think this one works if you start it with a 2a - if it does work, the timing is really tight by the end, and I've not been able to land it. I use it by fishing with 2b, and hit confirming into 5c on counterhit as the 2b forces stand (0 magic, 1 super, 2.51k).
2b > 5c > 2c > 623a > 5c > 2c > 3c > j.a > j.b > 5c > 2c > 3c > j.c > j.236a > j.b > 6a > 214c > 5c > 214b > super
Arizona's super has a massive amount of recovery. I put this together to demonstrate that you can block, put out a 236c, and still punish. You have to stagger the first 5c > 2c > 3c as much as possible to make sure the 236c hits before the 3c, otherwise Arizona won't get launched (3 magic, 1 super, 2.99k).
236c > 5c > 2c > 3c > 1d > 236c > 5c > 2c > 1d > 5c > 2c > 3c > 1d > 236b > 5c > 2c > 214c > dash > 5c > 214b > super
And finally, the least practical combo. There's almost certainly more optimisation that can be done here to get the damage numbers up some more, but it's too annoying to execute and I can't be bothered playing with it any more.
Not sure if this is a bug or Working As Intended... (6 magic, 3 super, 4.56k)
236c // 5c > 2c > 3c > 1d > 236c > 5c > 2c > 1d > 5c > 2c > 3c > 1d > 236b > 5c > 2c > 3c > 1d > 5c > 2c >3c > 1d > 5c > 2c > 3c > 1d > 214b > super > 214b > super
So what's happening here is the 236c and the 5c are both landing with a counterhit on the same frame. The game treats them both as the first hit, and they both get counter hit bonuses, and something seems to be going wrong with the juggle decay for the rest of the combo but I'm not sure exactly what. Anyway, it lets you loop the combo for much longer than normal, and with the huge damage spike from the double counterhit you can get massive damage. The lowest health characters in the game have 4.8k health, so with some improvements I'm pretty sure this could be the world's least practical touch of death combo.