Meterless mid screen max damage combos:
Jip, B2(charge a bit), B1, lift, jk, tp, jk, tp, d1, TKP. It deals 50% or 52% dmg, depends on the charge of B2.
Jip, B114, lift, jk, tp, jk, tp, d1, TKP. It deals 50% dmg.
Jip, F114, tp, 22, lift, jk, tp, d1, TKP. It deals 41% dmg.
Jip, 31, lift, jk, tp, jk, tp, d1, TKP. It deals 43% dmg.
Jip 12, lift, jk, tp, jk, tp, d1, TKP. It deals 41% dmg.
One bar mid screen max damage combos:
Jip, B2(charge a bit), B1, EX lift, jk, tp, jk, tp, d1, TKP. It deals 54% or 56% dmg, depends on the charge of B2.
Jip, B114, EX lift, jk, tp, jk, tp, d1, TKP. It deals 53% dmg.
Jip, 31, EX lift, njp, jk, tp, jk, tp, d1, TKP. It deals 48% dmg.
X-RAY mid screen max damage combos:
Jip, B2(charge a bit), B1, lift, jk, tp, dash forward, 22, X-RAY. It deals 61% or 63% dmg, depends on the charge of B2.
Jip, B114, lift, jk, tp, dash forward, 22, X-RAY. It deals 60% dmg i think.
jip, 31, lift, jk, tp, 22, X-RAY. It deals 49% i think.
Ermac's best punish for roll animations (except Mileena's roll and Raiden's Superman):
B2(charge it), B1, lift, jk, tp, 22, TKP. It deals 48% dmg. Damage could be increased if you do double jk tp combo, but its a bit tricky.
AA combos: standing 1, jk, tp, jk, tp, d1, lift, dash forward, B2, B1, TKP. It deals 38% dmg. You can also use B12F1 instead of B2, B1.
In general, dont use meter at all except if you are going for the killing blow. Better save it for breaker or X-RAY. Those are the combos i use mostly. In the corner i always go for B12F1 loops. Without meter its a bit tricky to pull it off, cause you have to know the height, but if you get the hang of it, its gg's and the damage is highly rewarding. You can also visit
http://testyourmight.com/threads/maximize-your-ermac-damage.9803/ for more info on his other strings, although they are not so damaging as the ones i suggested above.