Pokemon Evolution--Groudon, a legendary Pokémon that cannot fly

Mewtwo itself doesn’t have a regular evolution. Mega Evolution of Mewtwo, also known as Mega Mewtwo, is a powerful transformation that Mewtwo can undergo by using a Mega Stone. In this form, Mega Mewtwo's psychic powers are greatly enhanced, and it gains a significant boost in both its Special Attack and Special Defense stats. Its appearance also changes, with its body becoming more angular and its tail splitting into two. Mega Mewtwo is a formidable opponent in battle, capable of taking on even the strongest of foes.

Rayquaza is said to have lived for hundreds of millions of years. Legends remain of how it put to rest the clash between Kyogre and Groudon. ☁【Lethal skill】 Rayquaza flies to the sky while bringing its enemies in a row along, before releasing its massive power. It also makes peace with the target's aggression: locking into the target's rage for 1 round (rage level remains unchanged when locked in)

The reason why I specifically mentioned that it cannot fly is because of a funny scene from the 18th Pokémon movie, "Hoopa and the Clash of Ages." In this scene, Hoopa mischievously teleports a bunch of legendary Pokémon together, and after a series of events, Arceus appears and calms down the angry Pokémon. Everyone goes back to their respective homes, and then there's a shot of all the legendary Pokémon flying away, except for Groudon, who is left standing alone on the sea.