Using the argument that he should without making a crt would have to mean we take it with a grain of salt for now.
Morgoth has some pretty decent conceptual manipulation, as he himself was the first conceptual creation of Eru Illevetar.
He can likely just create a concept and incapicitate Bill either by saying he himself is now in the concept of "Nothingness" where he no longer exists.
Or he can create the concept of another universe, and seal bill in it.
It is a pretty nlf power.
But I guess to counter my points, Bill has actual showings of power at this level so it is likely just a match between hax vs ap.
I have to go Morgoth.
Bill hurt a grand total of maybe one person in the show who was non corpreal. It is not in his character to do so instantly and even then, I have doubts he can do it in a fight.
Morgoth, even if he was the weakest Low 2-C in the world, still has conceptual hax and saying he should be resistant to it is not the same compared to actually being resistant to it.
Considering also his 'song' created discord as well as warping the universe to bend to his whim by creating this concept, which mind you is being led by
this guy and 14 other dieties, shows just how powerful his concept hax is and how powerful it can be considering he can warp the reality of the universe itself.
Bill's only saving grace is he can manipulate time and stop it, but if we are going by in character.
Bill toys around and underestimates his opponents and lost to
this twelve year old boy.
Morgoth doesn't. Generally speaking.
Morgoth via reality warping likely being better and conceptual manipulation.