It goes Khorne, Tzeentch, Nurgle, Slaanesh in awakenings and that's pretty much how it is in terms of consistent power as well.*Taking into account CotE's point that time is a bit insane in the warp:
I believe (correct me if I'm wrong), Khorne was the first* of the gods to fully awaken. Can't remember where I read/heard that from though.
I'd guess Nurgle would have been next*, followed by Tzeentch. It seems to me that despair, depression, fear(?) and all those other lovely things Nurgle stands for would have been more prevalent in the past*, rather than the elaborate planning, scheming and hope that Tzeentch likes. But that's just my take on it.
Unlike Khorne I don't think it's ever stated whether Nurgle or Tzeentch awakened first*.
Slaanesh's power source will always wane before any of the other Gods, for when pleasure and self-indulgence has run it's course violence, despair, and change will remain.hm would explain why Khorne and Slannesh dislike each other aside from the obvious the younger in my opinion seems to be on a par with the blood god power wise with murder closley linked to sex and drugs, violence the same and blood definatly the same just my opinion