Unown !

Once during your turn, when you put Unown ! from your hand onto your Bench, you may flip a coin. If heads, put 2 damage counters on 1 of your opponent's Pokémon. If tails, put 2 damage counters on 1 of your Pokémon.

Flip a coin. If heads, this attack does 10 damage plus 10 more damage. If tails, Unown ! does 10 damage to itself, and this attack's damage isn't affected by Weakness or Resistance.