Thundering Raiju
Creature — Spirit
Haste
Whenever this creature attacks, put a +1/+1 counter on target creature you control. Then this creature deals X damage to each opponent, where X is the number of modified creatures you control other than this creature. (Equipment, Auras you control, and counters are modifications.)
Xavier Ribeiro
Rulings
A creature with a counter on it is considered modified no matter what kind of counter it is or which player put it on that creature.
(wotc • 2022-02-18)
An Aura controlled by an opponent does not cause a creature you control to be modified.
(wotc • 2022-02-18)
A creature that is equipped is considered modified no matter who controls the Equipment that's attached to it.
(wotc • 2022-02-18)
Rulings
A creature with a counter on it is considered modified no matter what kind of counter it is or which player put it on that creature.
(wotc • 2022-02-18)
An Aura controlled by an opponent does not cause a creature you control to be modified.
(wotc • 2022-02-18)
A creature that is equipped is considered modified no matter who controls the Equipment that's attached to it.
(wotc • 2022-02-18)