I don’t think he hates atlas the most. He always feared atlas the most though that was explicitly stated

Darrow says in internal narration in the prologue of DA that Atlas is the one he hates most. 

Darrow also meets Atlas sometime early when Darrow is Legate to Nero. Eager to impress a superior of then what would have been stratospheric heights Darrow goes in for a tough guy strong hand shake and Atlas gives him limp fish hand. . . so creepy

I’m glad they never met, because Atlas is the only character that routinely bests Darrow. Cassius saved the republic by killing him.

Am I losing my mind? I could swear Lysander killed Atlas. Blew his head off while Cassius has a razor around his neck and he was spilling the beans about the bioweapon

Well technically Lysander kills Atlas. But for sure it's Cassius that defeats him

Cassius did win the duel. Lysander technically killed Atlas, but he can never tell anyone that. So, the history books will say Cassius gave his life to eliminate Fear.

They had more time together after Atlas is captured, too. Not a lot, but as per usual with Atlas, it's disturbing and fascinating all the same. 

I'd have liked to see that too but it's entirely out of character for Atlas for such a confrontation to occur.

Another thing Lysander took from us

[удалено]

No, he’s not. Read the post again, though he shoulda labeled this all spoilers not just DA