Ok, this isn't known to everyone, but some elements have upperhands to others...Lemme show you:
As you can see, this does not include Light and Dark. This is because these are special Elements, that you have to decide which is better.
DARK-Powerful
-Weak at support
-Monsters have a type of influence on you, meaning that you could turn into one
-Strong against Light MONSTERS
LIGHT-Weaker power
-Good Healing and Recovery Skills
-No influence by monsters
-Strong against Dark MONSTERS
As you can see, each are stronger in battle against the other, but in a PvP battle, these strength advantages neutralize, and a battle of no elements begin.