Seraphic Greatsword
Artifact — Equipment
Equipped creature gets +2/+2.
Whenever equipped creature attacks the player with the most life or tied for most life, create a 4/4 white Angel creature token with flying that's tapped and attacking that player.
Equip 
Craig J Spearing
Magic Online Promos (PRM)
• #86082Rulings
Seraphic Greatsword's triggered ability won't trigger if the equipped creature attacks a planeswalker controlled by the player with the most life.
(wotc • 2020-11-10)
Once the triggered ability triggers, it doesn't matter what happens to players' life totals before the ability resolves. You'll create an Angel token even if the player the equipped creature attacked doesn't have the most life as the ability resolves.
(wotc • 2020-11-10)
Although the Angel token created by the triggered ability is attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example).
(wotc • 2020-11-10)
Rulings
Seraphic Greatsword's triggered ability won't trigger if the equipped creature attacks a planeswalker controlled by the player with the most life.
(wotc • 2020-11-10)
Once the triggered ability triggers, it doesn't matter what happens to players' life totals before the ability resolves. You'll create an Angel token even if the player the equipped creature attacked doesn't have the most life as the ability resolves.
(wotc • 2020-11-10)
Although the Angel token created by the triggered ability is attacking, it was never declared as an attacking creature (for the purposes of abilities that trigger whenever a creature attacks, for example).
(wotc • 2020-11-10)