>Is there any *alterable* character trait that would make an AP
>more or less likely to instakill on a cleave?

Mostly, no. However:

>* Target's health at time of cleave?

Below a certain fairly high % of hp, cleave can't be attempted at all.

And then there's some special cases like Miraculous Foresight. Zo Buki might help you out too, but I can't swear to that without double-checking the specs.

So barring stuff like maybe the lucky edge, no AP is any more or less likely to have cleave success than any other AP.

Pretty sure there are size restrictions on cleave. Something like "he is too much larger".

Is this not the case?

You're probably right.

I meant assuming the cleave is even *possible*. If there were multiple size differentials (target 1 bigger, target 1 smaller) where cleaving is possible, then I would be asking whether one is more likely to result in an instakill than the other.