Rayquaza

Rayquaza is a dual-type Dragon/Flying Legendary Pokémon introduced in Generation III of the  franchise.

Character description
Rayquaza is a large, green, serpentine creature. It has red-tipped, rudder-like wings on its shoulders and down its body, and similarly patterned fins on the tip of its tail. Yellow ring-like symbols run across the length of Rayquaza's body and it has an additional yellow ring on top of its head. Rayquaza has two limbs with three-clawed hands, and two long, flat, horn-like structures on its head, with two shorter horns along its jawline. It has small, yellow eyes with black pupils, prominent pink gums, and two discernible fangs in its upper jaw. While it is not known to evolve into or from any other Pokémon, Rayquaza can Mega Evolve into Mega Rayquaza if it knows Dragon Ascent, but only if it is not holding a Z-Crystal.

As a stage hazard
In Super Smash Flash 2, Rayquaza appears as a stage hazard on the stage Sky Pillar. After a short period of time, it can be seen flying across the sky in the background of the stage, and players are prompted to enter one of two areas to remain safe. Rayquaza then roars and quickly flies through the top or bottom of the stage, causing a large gust of wind to blow throughout the whole stage in the direction he flies in. It can also attack players, dealing 27% damage and strong knockback to players that make contact. The wind stops after Rayquaza disappears.

As a boss
Initially, Rayquaza was intended to appear as a boss in SSF2's scrapped Adventure Mode: The Flash Of Shadows. According to the original storyline, Rayquaza was captured by the villainous trainer Cyrus, who breaks into a stadium where and  are battling and has it fight Pikachu, Jigglypuff, and Zero. It is unknown how Rayquaza would have fought.