Well, I don't know how much of this is already known (too lazy to go through the whole thread~), but I've been grinding Senna in practice mode and have come up with some stuff.
Most damaging combo I could find meterless (that isn't the 214A loop), corner only. 6A starter seems to always miss Hanny at point blank. It may not be the best hitconfirm, but you get good damage from it if it hits.
6A > 5B > 2B > 5C > 2C > 236A > j.A > j.623C > link 5C > 623A
Highest with meter is mostly the same, can be done anywhere:
6A > 5B > 2B > 5C > 2C > 236A > j.A > j.623A > j.623D
And of course there's the default okizeme setup. Most commonly followed up by 41236C to encourage blocking, but you can probably just as well go for a mixup.
xx 2C > 214C > 2C > 214C > 2C > 214C or 6A
The more damaging version of the oki setup; requires good timing and doesn't seem to work at all on Nakanishi Sisters, Heita, Mecha Heita, Burai and Sanzou. Somewhat stricter timing is required on Rouga, Manbou and Agito midscreen, but they work fine in the corner.
xx 2C > 214A > link 5A > 214C > 2C > 214A > link 5A > 214C > 2C > 214A > link 5A > 214C or 6A
Maybe more to come.