Anointer of Valor
Creature — Angel
Flying
Whenever a creature attacks, you may pay 
. When you do, put a +1/+1 counter on that creature.
Light streaked down from the heavens, and a voice whispered in the soldier's ear: "You shall not fall today."
Antonio José Manzanedo
Rulings
Anointer of Valor's triggered ability triggers when any creature attacks any player or planeswalker.
(wotc • 2020-11-10)
If you choose to pay {3}, a second triggered ability triggers. Players may respond to that reflexive triggered ability before the +1/+1 counter is put on the creature.
(wotc • 2020-11-10)
You can't pay {3} more than once to put more than one +1/+1 counter on the attacking creature.
(wotc • 2020-11-10)
Rulings
Anointer of Valor's triggered ability triggers when any creature attacks any player or planeswalker.
(wotc • 2020-11-10)
If you choose to pay {3}, a second triggered ability triggers. Players may respond to that reflexive triggered ability before the +1/+1 counter is put on the creature.
(wotc • 2020-11-10)
You can't pay {3} more than once to put more than one +1/+1 counter on the attacking creature.
(wotc • 2020-11-10)