arceus lol. casually befriending the god of all gods is
if legerndaries/mythics are banned then probably any strong psychic type with teleport, that move would be cracked irl (not that it isn't already cracked). Not only for mundane tasks like traveling, but also for combat.
Steel types? teleport a flamethrower.
Dark types? teleport a flamethrower.
Other psychic types? teleport a flamethrower.
The geneva convention becomes merely the geneva suggestion.
Their psychic powers should be able to let them effortlessly perform any day to day activities. Just imagine a reunicus washing the dishes with its psychic powers, done in no time, Mitochondria™ Washing™ Machine™.
Top psychic picks, in no particular order, are as follows (guess who scrolled thru bulbapedia for an hour):

- 5000 IQ blah blah 135 Spa blah blah funny magic spoon blah blah, more importantly however, it would be able to connect to you as more than just a pokemon, since kadabras are children who turned into mons, "There are rumors that a child with mystical powers became a Kadabra" - PLA pokedex entry.

- Magic bounce is probably one hell of a cracked ability irl. its pokedex entries state that it is loyal, good at combat, and has a velvety texture to its fur. Basically a cat but better.

- "It brought rains by opening portals to another world. It was revered as a bringer of plentiful harvests." - Platinum pokedex entry.
OPENS
THE WHAT

- I have a 9 terabyte folder but i'm not going to tell you what's inside of it.

- Literal mfing supercomputer that can also do psychic stuff ITS SHINY IS SO FUCKING COOL. Its memory size is approx. 9 terabytes don't ask me how i know this.