Character not really mean one if he didn't use weapons of mass destruction.
That's the biggest plot hole in children's book.
However, he didn't have the technical expertise & money for nuclear option.
Biological & chemical weapon debatable if he had education which it never stated. The problem that more than even odds he will kill himself by accident.
Conventional weapons including guns & explosives? Same argument unless he buy off-the-shelf. However, that assumed he know gun safety.
He is a poster boy for gun control, small arms restriction & mental health check though.
I'm just playing Devil's advocate & being objective.
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How the Grinch Stole Christmas