A creature is legendary if it has the legendary supertype on its card , which represents a unique character or object in Magics story
This art really shows its power better than any other representation and gives it the justice it deserves from the little time it gets in Pokemon Scarlet
What are the most common weaknesses and resistances per type
It can do crazy things, whether its making tokens, dishing out +1/+1 counters, or even doubling up the loyalty counters Planeswalkers enter with helping them go ultimate (and often winning the game) in no time.
I was incredibly surprised at a few options going through the list such as K'rrik, Son of Yawgmoth and Hell's Caretaker both being horrors, which fit excellently in a deck like this
With 140 HP, Lapras ex isn't the most tanky, but Potion heals another 20 damage when used to ensure Lapras tanks attacks