Rank 4: Magnus the Red
As by far the strongest psychic among the Primarchs, Magnus the Red has the power to distort reality itself. His rise to Daemon Prince of Tzeentch has only further amplified these powers.
In war, Magnus’ magic is powerful enough to obliterate entire legions of attackers. Even against other Primarchs, he has a significant advantage. In combat against Roboute Guilliman, he almost achieved victory.
However, his power has a significant weakness: blanks. Mutants like the Sisters of Silence have the ability to fully suppress psychic power, rendering Magnus virtually defenseless, as he is pretty much the weakest Primarch in close combat.
There are also some Primarchs, like Leman Russ, who have special weapons or abilities against psychers to combat them. Russ is generally an interesting topic: The Primarch of the Space Wolves is probably to blame for Magnus falling to Chaos at all.
Nevertheless, Magnus’ powers confer upon him an almost god-like status – or would, if not for the fact that after his near-death experience at the hands of Russ, he “shattered” and his shards now each possess their own personality, powers, and abilities. Most have been reconstituted into a single entity, but not all.
