O-Kagachi, Vengeful Kami

Mana cost: {1}{W}{U}{B}{R}{G}
Type: Legendary Creature — Dragon Spirit
Power / toughness: 6 / 6
Set: Mystery Booster 2 #138 (mythic)
Price: $0.38 USD

Flying, trample
Whenever O-Kagachi deals combat damage to a player, if that player attacked you during their last turn, exile target nonland permanent that player controls.

O-Kagachi, Vengeful Kami has 4 printings, first in Commander 2017 (2017). EDHREC ranks it #8,593 among Commander cards. It appears most in Jared Carthalion decks (2,161 on EDHREC). 2 public decks on TCG run it. It has 3 official rulings.

Legality

commander: legal
legacy: legal
vintage: legal
pauper: not legal
modern: not legal
pioneer: not legal
standard: not legal
brawl: not legal

Public decks that run O-Kagachi, Vengeful Kami

Draconic Domination - Commander 2017, led by The Ur-Dragon
Painbow - Dominaria United, led by Jared Carthalion

Commanders that run O-Kagachi, Vengeful Kami most

Deck counts from EDHREC.

Jared Carthalion: 2,161 decks
Jenson Carthalion, Druid Exile: 1,673 decks
Kyodai, Soul of Kamigawa: 451 decks
Jegantha, the Wellspring: 181 decks

Often played with O-Kagachi, Vengeful Kami

Cards that show up in the same decks on EDHREC.

Rulings

2017-08-25: If O-Kagachi deals lethal damage to a blocking creature and also deals damage to its controller, that blocking creature is destroyed before a target is selected for O-Kagachi's last ability. It can't be exiled.
2017-08-25: A player attacked you if that player declared a creature as an attacking creature and that creature is attacking you. If that player attacked only planeswalkers you control, that player didn't attack you. If that player's creatures were attacking you only because they were put onto the battlefield attacking or only because you were reselected as the player they were attacking, that player didn't attack you.
2017-08-25: O-Kagachi's last ability exiles only one nonland permanent, no matter how many creatures attacked you or how many times that player attacked you during their last turn.