Evil levels him. More likely than Good (canon). This is assuming he can access Beast form. At which point he's a casual city buster. Even without it, he was generally more powerful than good Cole due to his lust for power.
I could go on, but I doubt I will. Now just to wait until Mercer advocates show up to claim he can one-shot God.
Sacred, the main issue is that with his city blast he'd also be blown up parts too given we know his durability, and.. wait.. can't remember what counts as a KO anymore. Because things like BFR can count, or even temp KOs.
Ruling?
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"Gonna need more chloroform..."
"If you look down on us, judge us, condemn us... then you shall fear us!"
Lol well its known that unless stated in the OP, a win consists of the character being incapable of battle. Death, KO, BFR, lobotomized etc. But the time it takes is iffy.
If regenerators take time to reform, thats usually fine. But when others do (like Raziel being killed and send to the spirit world, allowing him to return once he finds a corpse lying around) its not considered, at least rarely.
__________________
"Gonna need more chloroform..."
"If you look down on us, judge us, condemn us... then you shall fear us!"
With Raziel, his spirit actually leaves the battlefield and it can take several minutes for him to get back to where he was. Even so, if there are no corpses around for him to possess, and no spectral realm portals (which were provided by the Elder God) he's pretty much out of luck.
Mercer's regeneration doesn't take nearly as long and can be done without leaving the field, so I'm more inclined to let it slide. However, he also seems to need some biomass to kickstart the process if he's almost completely destroyed, so if there isn't any I'd say he's out of luck, too.