For Ermac, GM is a good option, but I'd use Cryomancer. Ermac is the poster boy for unsafe mix ups and Cryomancer punishes harder, regardless of screen position. Not only that, but Ermac can ignore/ punish many ice clone set ups leaving GM with ~25% per punish. Cryomancer is ~33%, meaning we've gotta hit him 1 less time.
Inferno Scorpion, I'd use either. Cryo has a better anti air option via d2 sword, but Scorpion can really only beat clone with meter, and they know it. Not only that, but corner clone, njp beats his ex teleport and you can put him right back in the corner behind clone.