In the Raven Guard novella Corax: Soulforge, Corax takes on and destroys two 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?
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 Daemon Primarch. I also know that Fulgrim killed Ferrus Manus but again a Daemon helped him to do that. I will accept post-Heresy examples (I know Vulkan appears in The Beast Arises series and Guilliman has returned to the 42nd millennium).