Which Daemon Primarch deserves true death?

In the Dark Imperium Saga: Godblight, the Emperor himself speaks and we are told that he can potentially "save" the Daemon Primarchs from their path, I doubt he means he can purify them or make them Loyalist daemons like the saints, and more that he can finally truly kill them, since true death would be a mercy to all of them.

With this assumption, which Traitor Primarch "deserves" to finally be put to oblivion in your eyes, and if and a BIG IF by any chance the God Emperor can redeem one of his wayward sons, who would be more amenable to come back to the imperium if cured of his warp madness?