Dang, I would not have expected that to be Mitsuhiro Arita, haha. I’m currently watching a YouTube series of someone who collects all Mitsuhiro Arita cards, so I’m already curious what he’ll say about this one when he’s at that point. 
But great idea @dizzylochs . I’ll go with Naoyo Kimura, since he made my favorite artwork of all:
He’s also well-known for the Tropical Island set (halve of the Southern Islands set) and for example the Neo Revelation legendary dogs:
Or the Light Jolteon and Wigglytuff of Neo Destiny:
I love his color contrast on his cards, and also how all the Pokémon are never in a stale pose. He really captures the Pokémon in their natural habits, while at the same time having both the Pokémon and background as a single artwork look absolutely amazing.
As for his worst artwork, I’d probably have to give it to this one:
It’s not really bad, but there isn’t much going on. Just the Pokémon in the water. Of course that’s its natural habitat, but it’s just a bit lackluster compared to most of his artworks.
Oh, and looking at all his artwork made me realize he made a lot of artworks that stood out to me in sets. If I didn’t already had so many collection goals, I would have picked up collecting all his artworks, lol. Damn you, Loch. 
(Unlike a lot of other people I never really look at all cards made by a single artist and am also pretty bad at picking up the illustrator from an artwork alone (except for obvious ones like Yuka Morii or Asako Ita). I definitely should look at lists of a single illustrator I like more often I realize. 
)
Greetz,
Quuador