Angel of Destiny

• WOTC Official Reminder Textofficial rules
  Double strike — This creature deals both first strike and regular combat damage.

• WWizards of the Coast2020-09-25
  Official Ruling
  If a creature you control somehow deals combat damage to you (most likely because its combat damage was redirected), you gain twice that much life as a single life-gaining event.
• WWizards of the Coast2020-09-25
  Official Ruling
  In a Two-Headed Giant game, Angel of Destiny's last ability can trigger as long as your team's life total is greater than your team's starting life total by 15 or more life.
• WWizards of the Coast2020-09-25
  Official Ruling
  All first-strike combat damage is dealt at the same time, and, separately, all regular combat damage is dealt at the same time. If one of those amounts of combat damage is enough to cause the player being dealt damage to lose the game, Angel of Destiny's first triggered ability has you gain life, but the other player has already lost the game and can't gain life.
• WWizards of the Coast2020-09-25
  Official Ruling
  If Angel of Destiny leaves the battlefield before your end step, its last ability won't trigger and won't cause a player to lose the game, even if Angel of Destiny attacked that player earlier.

Rulings via Scryfall