In order of death:
Nabriales: Killed by us and Moenbryda in 2.5
Igeyorhm: Killed by us with Nidhogg's eye in 3.0
Lahabrea: Killed by Thordan in 3.0 in the same cutscene
Altima: Implied dead in 4.3, as their mask has been claimed by Gaius.
Deudalaphon: Implied dead in 4.3, as their mask has been claimed by Gaius.
Emet-Selch: Killed by us in 5.0
Elidibus: Killed by us and trapped in Syrcus Tower on the First by G'raha as of 5.3
Mitron: Dead as of 5.4, after the Eden raid series.
Fandaniel: Killed by us in 6.0
Loghrif: Alive, as Gaia.
Halmarut: Alive, duh.
Pashtarot: Unknown.
Emmerololth: Unknown.
So at the absolute most, there are 5 remaining that may be a problem, and that is if both the two Gaius supposedly killed return. I'm doubtful of that, but it's not impossible that Elidibus recruited replacements for them between 4.3 and 5.3