So managed to poke around with K' today and figured out a combo that gets close to 800 dmg in HD for one bar. I don't know what else to cram in to make it break the barrier.
Midscreen/Semi-Corner
hop C, st.C(1 hit), f+A, {HD Bypass: hold back}, far st.D, qcb+Kx2 (instant slide), dp+A(1 hit), {HDC} qcb+K, qcb+K (whiff), (dp+A(1 hit), {HDC} qcf+C, f+D, f+A, qcb+B)x3, dp+A(1 hit), (HDC)qcf+C f+A, qcf,hcb+P = 783 dmg
If you can do j.C into d.C, f+A, it might push K' HD combo into the 800 mark, but I can't do that.
The minute spike after f+A, you don't need to do the whiff follow up. You let them fall to the right height and pop them back up again. Saves input stress and is easier to execute surprisingly!
HD mode ends exactly at the last HD cancel. This works about midscreen, it's not a full wall carry.