Red is so awesome, he foiled Giovanni's plan before it even started.
In Mt. Moon, the Rockets were trying to resurrect powerful fossil Pokémon. You stop them there and take one yourself.
At Celadon and Pokémon Tower, they were trying to use the Silph Scope to catch Ghost-type Pokémon, which Psychic-types are weak to. You stop them there and take the Silph Scope, rescuing Mr. Fuji.
At Silph Co., NPCs say that Giovanni is after the Master Ball, which can catch any Pokémon. You stop them there and get it yourself.
Giovanni is revealed to be the Viridian Gym Leader and possesses the Earth Badge, which makes any Pokémon obey you. They were trying to weaken and capture Mewtwo, and Red stopped him before he could begin.
Blue beating the Elite Four before you and becoming the Champion, taunting you about being the most powerful trainer in the world.
The first time you beat the Champion and cement your place as the best trainer in the region.