Sorry Ultimate Cloud, it's not right, although it's good to have someone who can reason out their answer.

Anyway, I'm gonna do a summary of the riddle so far.

The Riddle

Confluence designed
With life in mind
Climax then crescendo
A non-complement to the green hue
Reversal the key to resolution

Incorrect Answers
Soldier Heartless
Green Rhapsody
Heal Stomp
Stitch
Tinkerbell
Roxas' Dream Sequence
Rare Truffles
White Mushrooms
Green Requiem
Stealth Sneak
Cure Spells
Fire Spells
Potions
The League of Disney Villains
The Underworld
Reaction Commands
Opposite Armour
Dieing in a Boss battle
Any Keyblade
The final battle against Ansem
Dusk Nobodies
The Doppelganger
Hollow Bastion
End Of The World
Destiny Island
The world fragments at End Of The World
The Hearts of the World
Sephiroths Masamune
Kurt Zisa
Phantom
Green Trinities
Locking the Keyholes
The Green pillars if light in End Of The World

Hints
It is not in Space Paranoids
It is from Kingdom Hearts 1
It's not a Heartless
It's not a Keyblade
It's not a Song (So I haven't mentioned any in the wrong answers section)
The word "Reversal" can be replaced with "Opposite" depending on how you look at it.
One of the lines does not refer to the answer, but is a guide to solving the rest of the riddle.
The answer 'End Of The World' is extremely close in a way.

Hope that helps.