In the Ravenguard Novella Soulforge Corax takes on and destroys 2 defilers on his own.
I have been trying to think of a situation where a Primarch has been shown to equal or better this kind of ability in combat? Are there any combat scenes in the Horus Heresy books that show Primarchs being able to better this feat?
note :- I am looking for examples of Primarchs without assistance from the Warp. I know Angron survived a Warhound titan standing on him, and lifted the titan up. But that was after he turned to a demon primarch. I also know that Fulgrim killed Ferrus Manus but again a Demon helped him to do that. I will accept Post Heresy examples (I know Vulcan appears in the beast Awakens series and Guiliman has returned to the 42nd millennium)