Board Thread:Warhammer 40k General Discussion/@comment-27642965-20160211003725/@comment-26420219-20180613084138

That’s why Tzeentch has a cabal of 49 Duke of Change siffting through Kairos prophecies, and yes, Tzeentch is a time warper, he sends Lorgar to the future to witness Magnus after the Burning of Prospero, he also sends Ahriman back to the Unification Wars so he may claim one of the artefacts to bind Magnus’ soul-shards back together (The Crimson King).

Khorne is currently the most powerful Chaos God for three reasons:

1) As explained before it is Khorne’s hatred of Psykers and magic that render himself and his daemons impervious to psychic powers/magic (Realm of Chaos : Slave to darkness). A Bloodhound gains his immunity to magic because his Iron Collar was infused with a fraction of Khorne’s hate. As for the Black Templars and their "Abhorr the Witch" Khorne’s hate is so absolute that it effectively negates all magical/psychic powers. Since Tzeentch favoured tools are spells but Khorne is immune to it he is ascendant.

2) Why he occasionnally fights his brothers or mettles in mortal affairs, Tzeentch is not really playing the game. Throughout all Codexes Tzeentch is always described as a schemer that has no obvious plan because his attention is fixed on other realities than only the Warhammer 40k galaxy. (And there are also some parallels with Palace of the Plague Lord)

3) Khorne’s superiority is intended by GW; he is the God of War, fuelled by hatred and bloodshed "and in the grim darkness of a far future there is only war".

While what you may say about the effects of the Flood-spores on living organisms might be true and may thus be considered "superior" to Nurgle’s Rot, Nurgle’s plagues, including the Rot are only a tool to a different end: causing enough fear and despair so that the fabric of reality is weakened enough to cause a daemonic incursion. And once daemons are involved the Flood and the Forerunners are no match for them.