How do you get arcticuno back if you accidentally kill it?

If you accidentally defeat Articuno in Pokémon games where it appears, such as in the original Pokémon Red/Blue or Pokémon Let's Go, you can reset the encounter. Simply save your game right before battling Articuno, and if you accidentally knock it out, you can reload your save to try the encounter again. In games where Articuno is encountered in specific locations, you may need to leave and re-enter the area to respawn it.