So, starting from the top left, to bottom right, I think it's:
Lion El'Johnson, Fulgrim, Perturabo, Jaghatai Khan,
Leman Russ, Rogal Dorn, Konrad Curze, Sanguinius,
Ferrus, Angron, Roboute, Mortarion,
Magnus, Horus, Lorgar, Vulkan,
Corvus Corax, and Alpharius Omegon

Alpharius Omegon definitely look the cutest out of the bunch.

They all have a full head of hair, is the biggest difference.

The standouts to me are Lorgar, an "Onee-sama~!!" simp-minion who turns yandere, and Alpharius Omegon, the deadpan twins who troll everyone.

[deleted]

Oh, I've just realized they're in order by legion number.

And here we have 20 Girls who all got screwed over by their daddy being simply the worst parent in the galaxy.
Yes, even the loyalist ones. Except maybe Rogal Dorn if we don't count post heresy.

MarchofWaif said:

And here we have 20 Girls who all got screwed over by their daddy being simply the worst parent in the galaxy.
Yes, even the loyalist ones. Except maybe Rogal Dorn if we don't count post heresy.

19 (counting Omegon), remember there is 2 less who were deleted from history.

wheres the standalone art of horus though?

There's a big mistake in the tags : Alpharius and Omegon are reversed.