Grand King Ghidorah should have been in Godzilla series instead of mothra

the Mothra trilogy takes place in an alternate continuity not the heisei Godzilla universe, also almost every ghidorah is whay stronger than its godzilla counter part

Grand King Ghidorah is still just King Ghidorah. The "Grand" in his name was just put in the English dub for no reason in some scenes. The version of King Ghidorah in that movie has some interesting new powers, but he's actually much smaller than he normally is when fighting Godzilla.

The term "Grand" King Ghidorah was actually around long before the dub (which admittedly I have not watched). But as far as I can tell it's just used to differentiate the character from other King Ghidorah incarnations, or even the Cretaceous incarnation in the same movie.

He has some interesting powers, but they seem to be tailored for the Rebirth of Mothra trilogy's fantasy elements. (Such as mind controlling.) But he is one of the smallest King Ghidorah incarnations. Only 11 meters taller than the GMK King Ghidorah.