This is my first theory, so I hope you can find it interesting to read.
From what we saw, we now know that:
- Mib Can shape-shift.
Who is one who fulfills Biblical prophecies concerning an adversary of "The Chosen One" while resembling him in a deceptive manner?
- MiB can grant wishes.
It's clearly that MiB will seemingly provide for the needs of the people but deny the ultimate salvation.
- Lost has religious directions that include Christian, Islam and other religions ..that maybe means the MiB was mentioned/known in all those religions.
- Mib is stuck into Lock shape and unable to shift to another face? (Still able to be in Somky form thought).
I guess that because John was the "Only One" who wont leave, and accept to protect the island among all the others candidates. So unless there's another one decided to stay and accept this mission, he will not be able to shape-shift.
Now if we remember the Lost poster that shows MiB "in place of" John Lock, I can safely now assuming that the "Only One" has all this abilities together is: The AntiChrist, Al-Dajaal "in Islam".
"Antichrist" is the English translation of the original Koine Greek ἀντίχριστος, pronounced än-tē'-khrē-stos. It is made up of two root words, αντί + Χριστός (anti + Christos). "Αντί" can mean not only “against” and “opposite of”, but also “in place of"!!
PS: The words antichrist and antichrists appear "FOUR" times in the First and Second Epistle of John.!!