How is the MONSTER the true monster in Mary Shelley's Frankenstein?

The monster acts like an evil creature in the novel
Frankenstein when he decides to avenge his creator, Victor, by
killing all of his loved ones.

No matter how blindsided
Victor had been, his wish to create a living being was a result of his hungry ambition,
and not a pre-meditated nor evil plan to ruin someone's life. Victor had no idea what
the consequences of his actions would be, and there is no way to judge him based on the
gravity and the magnitude of what he did. In other words, Victor had no cannon to go by
as to how to treat his creation.

The monster, however, was
angry at Victor for having created him. He was also angry to be the way that he was, and
to be alone in the world. Although his anger is justifiable, the reality is that his
creation was a freak of nature, and so was he. Victor did not plan for that to happen.
Yet, the monster bypassed this reality and chose a very cruel way to avenge
Victor.

First, in what must have been a gruesome scene, he
killed Victor's little brother, William. Killing a person is bad enough, but killing a
child is unpardonable. It is attacking the truly innocent and that is indeed
monstrous.

Second, with utter premeditation, he set up the
child's caretaker, Justine, so that she would be blamed for the death of the child. She
was found guilty, and eventually died in the
guillotine.

Third, he killed Clerval who was Victor's best
friend and childhood companion. Clerval was also an innocent person who had a lot to
give to society. His death was indeed a huge blow to
Victor.

Finally, when the monster killed Elizabeth on her
wedding night, it displayed its biggest act of revenge and demonic anger. Why not just
kill Victor and spare all the innocent people? What the monster wanted was to make
Victor's life a nightmare, and he definitely achieved that. Yet, what this shows is that
the monster had a bigger capacity for hatred than Victor. Victor might have made one
huge mistake, but the monster caused the cruel and unnecessary deaths of multiple
persons. That is enough to establish that the monster was indeed a true monster in the
story.