what if i pass focus

Yes — passing Focus hands Focus and Priority to your opponent, and it doesn't end the Showdown unless they pass too (Rule 348).

They can play an Action or Reaction, activate an ability, or pass back. If they play something, you don't get your "pass" back — once that chain resolves and the state returns to Open, Focus automatically moves to the next player in turn order (Rule 346), so the Showdown keeps going as long as anyone acts. Note the pass that matters is the Pass action with an empty chain, not passing Priority mid-chain (Rule 347.2.a).

Once you both pass in sequence, it's a Combat Showdown → Combat Damage, then Combat Cleanup (which heals all units). A Non-Combat Showdown has no damage step or healing — if only one player's units remain, they establish Control and Conquer if they haven't scored there this turn.