Question

Who is the Mega Swampert Trainer in Anime?

Comments

The only one I remember is May's. Is there a different one?

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Could you elaborate? Do you mean in the actual anime, the Mega Evolution specials, or something else?

Answer 1

Mega Swampert appeared in Volcanion and the Mechanical Marvel, under the control of Levi and Cherie. It's also worth noting that Mega Swampert appeared in Mega Evolution Special II and the Pokemon Omega Ruby and Pokemon Alpha Sapphire Animated Trailer, May owns a Mega Swampert.

Hope this helps!

Sources: This, and this