So my memory of OW@W is pretty hazy. I remember the sun dip, Clark trying to hold onto his humanity as he pulled Imperiex and Brainiac 13 through the time tube, and I remember Imperiex realizing that the thing that had felt "off" to him was his own essence left over from the Big Bang. But the details are vague. So how does this not constitute killing? I mean, we could say that as a universal manifestation Imperiex is beyond any mortal definitions of death, but he's blown (literally) across the entire universe, and the fact that he spends his entire existence trying to correct that sense of "wrongness" shows that he never re-assembles himself.
So if that's not dead, what is it?
Likewise, I'd also ask about Darkseid being put into the Source Wall. Again, not "dead" as we might understand it, but to me the implication is clear; the Source Wall is, at the least, a prison Darkseid will never escape from (until Clark frees him years later) and at most the end of everything Darkseid is, which sounds an awful lot like dead to me.
Not being contrary, just genuinely curious as to how you see it.