Based on official sources, this is Ash's Pikachu. (Although the event Hatchus were Hardy nature, most Ash's Pikachu events over the years have been distributed consistently as Naughty).

Pikachu
Ability: Static
EVs: lol idk
Naughty Nature
- Thunderbolt
- Quick Attack
- Iron Tail
- Electroweb

Also, based on a Japan-only serial code event for M20, his Charizard is Adamant nature. Going by in-show personalities, rather than Smogon-tier optimization, what do you think are the canon natures of the rest of his Pokémon?