Radiance wrote:That was due to his own power at the time, not through a failure of the Avatars..
Their system worked, as did everything they did.
So they kill off some demons, but not all and fail in the end. So their system and their methods are not a success.
Zankou is victorious by manipulating leo and the charmed ones.. although it could be argued he only enlightens them...
as William James said.. one only needs to find one white blackbird to disprove the law that all black birds are black. I have my demon and in fact others demons to disprove the implication the Avatars were a success.
On a side note...
I believe Zankou is meant to be 'uber' powerful. If the Source couldn't vanquish him and he was able to cause irreparable damage to the Source, add to that that the Source could only contain him and the Source is directly implied to be as powerful as an Avatar by the Elders, then further add to that Zankou is also able to take several blast's from piper as well as several full on hit's from leo (one being at full strength when he's an Avatar) as well as evade the avatars... then yeah he's a win until his eyes get too big for him.
Charmed ones are meant to be the most powerful witches/magic force of all time.