Charging Cinderhorn’s triggered ability doesn’t trigger at all if a creature attacked this turn. It won’t get a fury counter or deal damage.

Charging Cinderhorn’s triggered ability triggers at the beginning of each player’s end step if no creatures attacked, including yours, and even if it wasn’t on the battlefield during combat.

If Charging Cinderhorn leaves the battlefield in response to its triggered ability, it won’t get a new fury counter, but it will deal damage equal to the number of fury counters it had before leaving the battlefield.

If a player loses the game during that player’s own turn, the turn continues to completion. If no creatures attacked, Charging Cinderhorn will get a fury counter even though it won’t deal damage to any player.