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that is one way to look at it but it still contradicts right, if one ability is active the other is not
Complementing would be something like - Void and silence or amplify and thorn.

Yes, that is another version of 'complementing' abilities.
Contradictory would be something like Heal/Affliction or Immunity/Poison. Blast! and Deathblow don't actually work against each other it's more....
IF target has neighbors- do 1/2 damage to them too
If not, do 2x damage to the target

In boxing, I wouldn't say rights and lefts contradict each other just that you don't use both at the same time.

Affliction cannot be used on an allay, that won't be considered