harry potter - Could Avada Kedavra be used as a non-lethal attack?

In Goblet of Fire, Mad Eye Moody

Or rather, Barty Crouch

explained the 3 unforgivable curses to the 4th year children. He explains that Avada Kedavra needs a "good deal of magic behind it" for it to be effective and that all the students combines at their current proficiency "[wouldn't] get so much as a nosebleed".

Could a wizard/witch then not put much force behind AK and purposefully not kill someone but just harm them tremendously?

Answer

I don't recall any canon evidence, but based on fake-Moody's "I won't get so much as a nosebleed", odds are it's more of a binary thing: if your magical energy and mental states are above some threshold, Avada Kedavra will work, and if not, it will fizzle.