What is the highest AP

Jokes aside, I don't know the exact calculation, but it probably involves

Among other things like a teammate with Zeke's

x5 (they stack) + + on Ryze,

if you were trying to gain the most ap as possible, archangel staff moro, -deathcap, then the items you had named

Probably Viktor since Hexcore can provide 180 AP at max level.

I would say Thresh, but I assume anyone who can infinitely stack it is ignored.

It would have to be Ryze (passive grants AP based on mana, and mana based on AP) decked out with...

and fully stacked and

Wouldn't a fully stacked be up there too? I don't play her much, just recall her passive was basically an extra