The Legendary Axe Genzaniku has an affix "Summon a Fallen Champion" but after some searching I haven't been able to determine his damage. I don't see any explanation on the official blizzard page.
When I first equipped this item, I noticed that he "one-shotted" something that my character could not kill in one hit.
Is his damage fixed, tied to my damage stat as a percentage, or is he just a Fallen Champion tied to my (or my weapon's) clvl?
{edit} I no longer have this weapon, so it is not possible for me to test it myself currently.