Why don't Kanaxai's Aspects die...

So I was doing the deep with my perma sin using the dagger variant with horns of the ox included for KD. So i was doin my shiztaz and bam bam got kanaxai aspect of soothing down to 1hp but thats it,he never dies...help pls?

did you knock him down at 75%,50% and 25?, maybe he went from 25% to "1 health" with degen and you have to knock him down again

Well I didnt' bring horns of the ox for fun, yes I did KD him at the right times and I have no degen in my build just pure damage. He's on his last bit of heath but doesn't die despite even more KD's