Froslass ex anti Charizard ex

A simple Froslass ex (Paradox Rift) deck is also a good counter for the Charizard ex (Obsidian Flames) deck.

Strategy

Going second is the best choice with Arven (Scarlet & Violet) to grab Battle VIP Pass (Fusion Strike) and Technical Machine: Evolution (Paradox Rift) or Rigid Band (151) or Supereffective Glasses (Astral Radiance) to complete your setup.

Also has a baby Froslass (Chilling Reign) in case there is an Entei V (Brilliant Stars)

Rigid Band (151) and Lake Acuity (Lost Origin) to tank the damage and Kricketune (Astral Radiance) to buff the HP(340HP effective total). Finally, after all this, if they KO your Frosslass ex, they flip a coin and might get only 1 prize for all those efforts, thanks to Evanescent ability.

or Supereffective Glasses (Astral Radiance)  for aggressive 1HKO to boost the damage for weakness.

Have fun! As usual, feedback is welcome.