I did find some improved meterless corner combos of some listed here. I've written them down arranged in damage/difficulty:
For f421 combos you can alternate depending on how well you can time them. Back Jump Punches are faster, so easier to combo off.
f421, forceball, bjp, fjp, 1, f421+slide - 31%
f421, forceball, bjp, fjp, 21, f421+slide - 32%
f421, forceball, bjp, fjp, fjk, f421+slide - 32% (landing a 1 after fjp doesn't add damage)
f421, forceball, bjp, d2, throw - 32%
f421, forceball, bjp, njp, 21, f421+slide - 33%
f421, forceball, bjp, njp, fjk, f421+slide - 33%
f421, forceball, bjp, fjp, fjk, 21, f421+slide - 33% (perfect timing)
f421, forceball, bjp, fjp, 3, f421+slide - 33% (perfect timing)
f421, forceball, bjp, d2, f421+slide - 34% (out of corner)
Now some with Back Jump Kicks.
f421, forceball, bjk, 21, f421+slide - 33%
f421, forceball, bjk, fjk, f421+slide - 33% (perfect timing, landing a 1 after fjk doesn't add damage)
For 2124, I got some good ones too.
2124, njp, d2, throw - 29%
2124, njp, d2, f421+swipe - 31% (out of corner)
2124, njp, 3, f421+swipe - 31%
2124, njp, fjp, fjp, 3, f421+slide - 31%
2124, n/fjp, fjk, 21, f421+slide - 31%
2124, njp, fjk, d2, throw - 31% (perfect timing)
2124, njp, fjp, d2, f421+slide - 32% (out of corner)
2124, njp, fjk, 3, f421+slide - 32%
2124, njp, 3, 21, f421+slide - 33%
2124, njp, fjk, d2, f421+slide - 33% (perfect timing)
Hope that helps. These were all tested on Ermac, I'm not sure if he's got a bigger hitbox than average. I may find more.