I believe I am the first person to complete a Rainbow Challenge. As you can see my team were massively underleveled except for my Starmie who was the MVP for the game The 4 moves it knew were deadly mixed with them all being Special based and Starmies high Sp.Atk, I rinsed the hell out of everyone. The reason that my Starmie jumps so many levels at the end is because I went straight into the Elite Foure without buying any items, then when I got to lance I sort of got messed up and ended up dying to a critical hit outrage.
Here is a picture of my adventure:
Nidoqueen. Level 50.
SuperPower - Earthquake - Mega Punch - Body Slam.
Parasect. Level 42.
Slash - Leach life - Spore - Poison Powder.
Arcanine. Level 52.
Flamethrower - Extremespeed - Strength - Aerial Ace.
Starmie. Level 60.
Psychic - Surf - Thunderbolt - Blizzard.
Electabuzz. level 56.
Focus Punch - Thunderbolt - Attract - Toxic.
Scyther. Level 49.
Swords Dance - Pursuit - Slash - Wing Attack.