Raid Bombardment

• WWizards of the Coast2018-12-07
  Official Ruling
  A creature with 0 power can attack, as long as it doesn't also have defender.
• WWizards of the Coast2018-12-07
  Official Ruling
  If the attacking creature leaves the battlefield before Raid Bombardment's triggered ability resolves, Raid Bombardment deals 1 damage to the player or planeswalker that creature was attacking before it left the battlefield.
• WWizards of the Coast2018-12-07
  Official Ruling
  The power of the attacking creature is checked only when the ability triggers. Once it triggers, Raid Bombardment will deal 1 damage to the appropriate player or planeswalker even if the creature's power changes before the ability resolves.
• WWizards of the Coast2018-12-07
  Official Ruling
  If you attack with multiple creatures with power 2 or less, Raid Bombardment's ability triggers for each of them separately.
• WWizards of the Coast2023-09-01
  Official Ruling
  Raid Bombardment's ability won't do anything when a creature you control with power 2 or less attacks a battle.

Rulings via Scryfall