There are many manga and manhhua where the mc is reincarnated as a monster so today we are gonna list them down here .
The usual isekai storyline where the average japanese man dies from exhaustion and was reborn as aslime in an another world but with a wish granted to have the ability great sage.
The story where the hero is reborn as a low class goblin who has to continuosly fight for his survival but with times he evolves and make his life full of misery to full of wealth and power.
korosensei the king of assasin and the teacher of class f who can even dest.roy the earth when he detonates
here our hero is not actually reborn as amonster but his soul has been transfered in the body of a dragon who was the strongest being in that universe and him turning himself from a dragon to human and fighting gods is all this story revolves around.
is there a problem if the demon lord is a goblin
This one is an average story line which most of time follows the story of re monster as the name already suggest the hero is a goblin who has turned himself into a demon lord with his levelling up and started his own harem.