In response to your ending note, I'd say that you succeeded, though I don't necessarily see Mike as a villain. Not a hero either, but someone realistic. If you've ever read the Count of Monte Cristo, you see a similar complex figure, who gets his revenge through some quite horrible means and then walks away from it to live a happy life.
Overall, I want to congratulate you on writing one of the most realistic revenge fanfics I've ever read, and for avoiding the unfeeling killer trope. Mike feels, he has empathy, but he also does whatever he feels to do. Congratulations on succeeding with your goal for this story.

On the one side this fiction is really brilliant: Mike is like a better Voldemort. He is a Ravenclaw through and through, highly logical, he has a goal and he makes plans to achieve it. He doesn't get caught, because he doesn't get emotional halfway through and let's himself be distracted by his feelings - as Voldemort did time and time again, be it rage, fear or simply arrogance. He also a manages to divide his personal life, Hariette, from his plan for revenge, knowing that he loves her too much to really hurt her.

To me the first chapter was almost perfect, if it hadn't been for the wrong use of the Imperius Cruse. The Imperius has to be constantly held by the Caster, which is an exhausting task. The moment the curse is not upheld anymore the victim remembers all that happened while they were under it. It can't influence people the moment it isn't actively used. Mike telling Neville to forget his glasses would have only worked if he had had him under the Imperius for weeks on end. Telling people what to do and then lifting the curse is not how it works.

I really enjoyed chapter two, because it showed even more of Mike's character and how he thinks. It's quite interesting to see how he goes through with agenda, even going so far as planing the destruction of Hogwarts years in advance. He sure had grand plans.

Scorpius nominating him for Minister of Magic was a logical conclusion on his part and funny as Mike really hadn't expected it despite it being obvious for the reader. I was really curious for whether or not - or better how - he would take the job but then...

I don't know, he suddenly ... went stupid? He's so highly logical, so pure Ravenclaw, all the time and then all of a sudden he doesn't understand why societies need governments. That really puzzles me. Of course there is stuff you cannot tell the average citizen; you can't simply not put regulations on things like anti-muggle wards in public health stadiums.

"Govern yourself" sounds, I don't know... like he wants to be an anarchist? Go back to the Stone age? How can you govern a society by not governing it? Less regulations, fine, but even then in the late 21st century... who would the British be able to trade with if they don't have or agree to uphold regulations? How will any other nation take them serious? This baffles me to no end.

The last chapter was a little mad, but after all these years of plotting, of murdering people and lying even to his wife he has every right to be a crazy. Lucky for Albus that he stayed clear of the Wizarding world for so long. Sad for those wife, though.

Tight prose and dry wit play well with grisly, and you do all three very well, indeed.

Mike did not commit THE MOST horrid crimes, though. I can think of worse ones.

Then again, I am imaginative...

I feel it necessary to point out that mike's ideas for reform are idiotic bullshit. To give one example, cauldron bottoms are important because a potion might eat it's way through one and explode, killing the brewer. And don't tell me nobody would sell a cauldron that bad, because that's bullshit too.

usually, warnings go at the front.

This is spectacular. Absolutely spectacular. One of the more thought-provoking pieces of fanfiction I've ever read.

To answer your question, you succeed perfectly. You've not only created a horrible monster, but the worst kind of horrible monster - the one with purity of motives. Lawful-Evil, if you will. He's such a rich character, but having to get into the correct frame of mind to write him so. freaking. perfectly. must have been a toll on you. Amazing, amazing work. Bravo again.

Dark Lord Dennis may be the favorite three words I've ever read in fanfiction. Also - holy shit. This has turned from a dark little piece about the ramifications of status quo in Magical society to an absolutely brilliant character study of a sharp but fatally warped mind. Bravo, sir. I can't wait to see how this one ends up.

Holy crap. This Mike fellow is no joke. What an amazing premise, and a deft beginning. Onward, then...

Wow. This one hell of a story. Dark, but at the same time ... there was hope that things would actually get better. Great writing. Keep up the good work.

Even though you killed off Harry, I think that this is one of the most interesting and amazing one shots I've ever read

would have cured - would have cured Marie (was lacking a subject)
murder - murderer
they had shared something personnel with Mike - they had shared something personal (unless there's a second Mike, it wouldn't make sense)

Sooner or later Murphy will show up.

Wouldn't someone find out in the future and then ruin his family's life as revenge? Mike basically became everything he hated.

Wow. I was rather hoping that Mike would get his come-uppance, but he seems to have got away with it. I like the idea of Dark Lord Dennis, and Mike learning from him that he needed to do away with the society he saw as corrupt rather than try to rule it. A very well thought out piece. I'd be interested to read a "what happened next".