So I got bored, and wondered how the Primarchs stack up against each other. Since they don't all have the opportunity to fight each other in the fluff, I used the rules sections from 1d4chan to make this chart.
NOTES:
- This doesn't include Psychic powers, so if you add those Magnus obviously jumps way higher, right into the top tier with Leman and Horus (which makes sense, he nearly beat Russ and the wolf is undefeated)
- Lorgar also jumps up significantly but he's harder to measure considering he's never truly beaten another Primarch in the fluff
- Russ is undefeated, which probably doesn't make sense considering Horus mortally wounded the Emperor. The rules have Horus pre-warp-steroids, so it's safe to say that Horus post-Molech can beat Russ
- I couldn't find matchups of Magnus against Guilliman or Horus. Without psychic, its safe to say Magnus loses both. With, Guilliman loses, Horus will probably lose (pre-Molech Horus though)
- Alpharius is truthfully the worst, not Lorgar because he can draw on psychic. Considering Alpharius lost a fluff fight with Dorn, who is also a low-tier Primarch, this makes sense (Alpharius is also described as the size of a large Astartes, so not very intimidating)
- This doesn't include the Lion, Sangiunius, or the Khan as they don't have rules yet. The Lion fought Russ into a close tie in the fluff, so he should be top tier (perhaps better than pre-Molech Horus)
- Sanguinius isn't really on record fighting any Primarch except post-Molech Horus, which could probably kill any Primarch. Still, he's awesome so probably middle-tier at least
- The Khan has beaten Mortarion in the fluff, which means he's probably mid-tier at least, though I doubt he's on the same level as Leman Russ
Anyway, maybe people will find this interesting!