Terminal Virus can’t be used on Atrahasis?
Bosses are immune to all instant death effects (Death Sentence, Death Revenge, Sudden Death, etc.)
Btw, this is the Hunter Island section. You are probably looking for the Neo Monsters section!
What about woolala passive
Hmmm, I remember bosses have innate Stun Immunity, but I don’t recall about any Sleep Immunity. Atrahasis opens the battle with a sure-hit Poison Gas on everybody, I didn’t even try going for sleep 
It shouldn’t work too. They are immune to health manipulation (like despairing wave etc.)