These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Michael is a cold-blooded Serial Killer with a hatred of teenage sexuality and a fondness for carving knives. After killing his sister at the age of six, Michael breaks out of prison as an adult and goes on a killing spree through his hometown of Haddonfield, on his way to kill his surviving sister, murdering three of her friends before targetting her. He's stopped, but the horror doesn't end there. Michael returns again and again, making numerous attempts on Laurie, her daughter Jaime, and anybody else who gets in his way. Incapable of feeling empathy, and driven by a loathing of seemingly everybody he encounters, the unstoppable and perpetually silent Michael helped to define the slasher as we know it, and remains one of the most bone-chillingly evil.
Dr. Loomis: I met him fifteen years ago. I was told there was nothing left. No reason, no conscience, no understanding; even the most rudimentary sense of life or death, good or evil, right or wrong. I met this six-year-old child, with this blank, pale, emotionless face, and the blackest eyes... the Devil's eyes. I spent eight years trying to reach him, and then another seven trying to keep him locked up because I realized what was living behind that boy's eyes was purely and simply... evil.
This is even the quote on the trope's page, at least partially.
Evil Is Sexy: When he's unmasked, Michael is surprisingly attractive.
Seinfeld Is Unfunny: Even though Michael Myers came first, in the later sequels, he ends up seeming like a rip-off of Jason Voorhees. Also since all the cliches Halloween created (or in some cases popularized) have now become cliches they are no longer frightening.
Special Effect Failure: When Michael smashes one of Marion's car windows, he obviously has a wrench taped to his hand.