Kulo Zakai -- all meritorious

From a private meeting between R' Shneur Chaim Gutnik and the Lubavitcher Rebbe (5 Menachem Av 55727/1967)

R' Gutnick: ...There is an inyan of b'ita and achishena, and it is stated in chazal (Sanhedrin 98a) that it is dependent on whether it will be a situation of zachu ("they merit") or lo zachu ("they don't merit") -- kulo zakai ("all meritorious") or kulo chayav ("all culpable"). Could it be that the Rambam says that it must be according to a certain order, yet in the words of chazal we see differently (that not necessarily does it need to be all meritorious")?

Lubavitcher Rebbe: Nu, how do you understand? Obviously the Rambam also knew these words of chazal that you know, and nonetheless this is his psak din [binding halachic decision] (that there needs to be [a king from the house of Dovid who will] "compel all of Israel, etc." -- kulo zakai).

Regarding what you are saying, that it appears [to you] that there could also be a situation of kulo chayav -- we see the Satmar, Harav Katznellenbogen and Menachem Schneerson will not allow this to happen. Additionally, regarding kulo chayav you have nothing to talk about and the only way is that it will be kulo zakai.