Card

Avacyn, Angel of Hope

Mana cost {5}{W}{W}{W}

Flying, vigilance, indestructible Other permanents you control have indestructible.

Part of 19 known combos, 8 of them two-card. 3 official rulings.

Bracket

B1 Exhibition — Not in the same deck as its two-card combo partners: Worldslayer, Nevinyrral's Disk, Magus of the Disk, Obliterate, Boros Reckoner, Lethal Vapors, Aether Storm, Worms of the Earth
B2 Core — Not in the same deck as its two-card combo partners: Worldslayer, Nevinyrral's Disk, Magus of the Disk, Obliterate, Boros Reckoner, Lethal Vapors, Aether Storm, Worms of the Earth
B3 Upgraded — Not in the same deck as its early two-card combo partners: Worldslayer, Obliterate, Boros Reckoner, Lethal Vapors, Aether Storm, Worms of the Earth
B4 Optimized — allowed: No restriction beyond the banned list
B5 cEDH — allowed: No restriction beyond the banned list

Two-card combo with Worldslayer, Nevinyrral's Disk, Magus of the Disk, Obliterate, Boros Reckoner, Lethal Vapors, Aether Storm, Worms of the Earth (early with Worldslayer, Obliterate, Boros Reckoner, Lethal Vapors, Aether Storm, Worms of the Earth)

Bracket: Lotus Vault analysis, with Commander Spellbook flags

19 known combos, 8 of them two-card.

Avacyn, Angel of Hope + Worldslayer
Produces: Destroy all permanents opponents control each turn, Lock, Mass Land Denial
View on Commander Spellbook
Avacyn, Angel of Hope + Nevinyrral's Disk
Produces: Destroy all creatures, artifacts, and enchantments opponents control on each of your turns
View on Commander Spellbook
Avacyn, Angel of Hope + Magus of the Disk
Produces: Destroy all creatures, artifacts, and enchantments opponents control on each of your turns
View on Commander Spellbook

2023-07-28 · Wizards of the Coast
A battle with indestructible still loses defense counters as it's dealt damage. If it's a Siege, it will still be exiled when the last defense counter is removed from it, and its controller may still cast it transformed without paying its mana cost.
2020-08-07 · Wizards of the Coast
Because damage remains marked on a creature until the damage is removed as the turn ends, nonlethal damage dealt to a creature you control may become lethal if Avacyn leaves the battlefield during that turn.
2020-08-07 · Wizards of the Coast
A planeswalker with indestructible still loses loyalty as it's dealt damage. It is put into its owner's graveyard if its loyalty becomes 0.

Rulings: Scryfall · Wizards of the Coast