This is just something I through together wihtout buying anything. Use the Galarian Corsola and Alakazam EX to spread damage counters and use evolution inscense and dark dragonite's ability to evolve a Gastly to a Gengar. Use Gengar's creep show to knock out opponent's pokemon. If you have ideas or tips write them in comments.
NEW COMBO
Get Radiant Sneasler into play
Get a gastly, then Crimson Invasion Haunter into play, then evolve into Gengar.
Attach a memory capsule to Gengar.
Gengar uses Sinister Fog put 1 damage counter on each of your opponents bench and poison on the active pokemon.
Radiant Sneasler increases the damage counter on the active pokemon to 3 damage counters.
Gengar uses Haunter's pain amplifier and increases all the benched pokemon's damage counters to 3.
Use Boss's orders to switch whatever pokemon you want into the active spot (because they all have 3 damage counters on them)
Use Gengar's creep show to knock out whatever pokemon you want in your opponents active spot.