@Hades0918 It's a challenge in Legends: Arceus where you have to complete a battle with only a single Pokémon. The opponent is often selected to counter your Pokémon in some way, and there are requests that require you to complete a few of them, Magikarp included. Magikarp's opponent is a Hisuian Electrode that only knows Self-Destruct, but in Legends: Arceus, Magikarp can only learn Splash, so your only option is to maximize its defenses and HP.
Not that anybody's going to see this, but…
Uh…
I've been working on completing all the research in Legends: Arceus. I already have the Shiny Charm, but I mean ALL the research.
I haven't been doing this a lot lately, but still.
The Wurmple line has been a bit annoying because of how many you have to defeat, despite their low spawn rate.