Alright, i'm gonna try and be as helpful as possible here.
Honestly the things that check and counter subCM meloetta change depending on what coverage moves its running (although there are a few universal ones). I've run defensive teams myself in the past and i've been able to get around it at least most of the time.
Some defensive/bulky offensive checks that can help out with subCM meloetta include:
Spiritomb (hard counter if resttalk Wow Foul Play, it even has infiltrator to burn/attack from behind the sub lol)
Specially Defensive Drapion (Tbolt/Psychic has major trouble, Hyper Voice can be annoying but you can still take at least one boosted one, phazes Meloetta, hurts it with Knock Off, and can set up Toxic Spikes once grounded poisons are down.
Standard spread Roar Rhyperior (beats both Psyshock Varients and Hyper Voice varients, boosted Psychic hurts quite a bit tho).
SpD Meloetta (takes everything and uses Perish Song to force a switch, no recovery but wish support from Aromatisse or Alomomola is really helpful)
Skuntank (See Drapion, although it exchanges phazing and tspikes for Defog and Sucker Punch)
Escavalier (Not exactly a stall Pokemon but it can work alright i guess, i mean Alomomola is a p. common sight on stall teams and the two pair together fairly well, not to mention Escavalier checks some other annoyances to stall teams, also gives you some offensive presence if you need it).
Hope i helped out at least a bit :x.
another alternative option to Drapion is running scarf w/ pursuit as kind of a gluemon to your defensive team, i've seen that used effectively by a few users before.
