Which ounce of logic even suggests there exists a parity, the Son and the Daughter 'threaten' the galaxy if released from Mortis. Which is absolutely miniscule compared to what the near-death God Emperor deals with daily, his psychic power has the mere side effect of incinerating ships over light years.
His blows can level planets and his psychic attack hit Horus with the power of an exploding sun and didn't simply destroy his body but annihilate his spirit, an attack that threatened to obliterate four multiversal Gods.
It was a physical contest where all the power of said Gods was stored in Horus' body, they abandoned his body in the last second otherwise their power would have been destroyed with it and would have left them severely damaged.
The God Emperor's mental prowess is such that in a near death state he is capable of maintaining a psychic barrier that saves the galaxy from being utterly annihilated in ways too horrific to imagine by the warp.
The Chaos Gods themselves destroy and create entire universes within the infinite warp on a whim every second, literal universes.
The God Emperor is still capable of outmatching them.
The rolling chaos of the aether was a playground for titanic forces, where entire universes could be created and destroyed with a random thought. How many trillions of potential lives could be birthed and snuffed out just by thinking of such things?
-Pg.712, Thousand Suns
Note this is in the context of describing the powers of the Chaos Gods, who for all intents and purposes are the literal and unliteral manifestations of the warp, which is an entire plane of paradoxical existence, fueled by every single emotion ever felt.
His feats must be taken into context, for example when fighting Horus he was under the illusion that he might save his son, so he wasn't even really trying to fight back. Horus himself has blows powerful enough to level planets, but is further amped by the full powers of the Gods, so the Emperor was letting Horus beat him nearly to death. The Emperor lost an eye and body parts, yet the guy easily one shots Horus when he realises he was beyond salvation.
Then in a near death state, the Emperor's mind flows through the Astronomicon, stopping the powers of those Gods from entering the galaxy.
Everything he has done is low tier for him, the only time we see the Emperor going legit all-out is when he kills Horus. This is a humble God, who doesn't even want to be called a God, he is conservative with his powers because not doing so would be entirely counterproductive to building a galaxy spanning empire.
Lol the emprah stomp !!
P.S : If that is throne emperor lost in luancy with his psychics scattered all around the warp, weaken by fighting hord of daemon + the hive mind.....
I would say the son..
And yhea the emperor is a warp god, but he is born because a lot of chaman committ mass murder to create him, cuz daemon were invading the materium and chaman were a bit powerless against that, so here we go they created the ultimate bad ass.
Also go watch this :
https://www.youtube.com/playlist?list=PLyiDf91_bTEgnBN0jAvzNbqzrlMGID5WA
https://www.youtube.com/playlist?list=PLyiDf91_bTEi8rS479vg0k-TjFh4iGf3g
https://www.youtube.com/playlist?list=PLyiDf91_bTEhDRwqQfqVwaKFeBaTVesHh