You cannot do OMB off A Coup, it misses. Unless I am bad.
For the corner, this works vs crouching, no counter hit:
5B > 2AB > B Coup > 2A > 2B > 2D > [j.B] > j.C > C Bufula > [5B] > 2AB > C Bufula > [5B] > 2AB > A Coup for 5011 damage.
The same combo works against standing as well if you start with [5B], of course, doing 5221. This is way more than any other meterless corner combo listed here off that starter. By the way, at this point the combo scales so much that if you end with C Bufudyne and they tech as soon as they can, they get hit by it after the tech and if they don't tech at all it combos. Good luck.
Same is of course true for a sweep combo, so off a non-counterhit sweep near the corner you can just go:
2AB > B Coup > 2A > 2B > 2D > [j.B] > j.C > C Bufula > [5B] > 2AB > C Bufula > [5B] > 2AB > A Coup for 4548 damage.
A significantly more damaging 2B counterhit antiair combo when you are a bit closer to the corner than midscreen and hit them deep enough with 2B is:
2B > [6B] > 2AB > B Coup > 2A > 2B > 2D > [5B] > 2AB > C Bufula > [5B] > 2AB > A Coup for 4495 damage. [j.B] > j.C > C Bufula version does 4353 damage.
By the way, here's my perfectly optimized Mabufudyne corner combo off [5B] FC. I haven't seen this exact one anywhere so hopefully it's not widely known:
[5B] > 2AB > OMB > [6B] > 2AB > B Coup > 2A > 5B > [2B] > 2D > [5B] > 5C(15) > Mabufudyne > 2A > Getsui Ei > C > Myriad Arrows B(hold) > C > D > (Kick gets released) > D Bufudyne
It does 10077 damage. You need to delay the C after the Getsui Ei so that all the ice doesn't land or it drops. Just the higher ice can land, the lower ice needs to whiff. It builds about 15 meter before mabufudyne so you can start it at 85 or so.