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.
YMMV: Final Crisis
Complete Monster: Do you really need to ask? At least Mandrakk has the excuse of being a vampire and thus a victim of The Corruption; he chose Darkseid specifically because he was the worst and most dangerous thing in the universe and one most likely to bring about the destruction of reality. When he gets round to doing just that its only because he's dying and its little more than a giant "FUCK YOU" to the heroes and the rest of Creation for stopping him, a mixture of If I Can't Have You and Taking You with Me on an omniversal scale. This is after he begun erasing The Evils of Free Will and nearly pulling a Grand Theft Me on the entire human race with the help of the Anti-Life Equation (so his billions of victims were in a state of soul-crushing misery to boot too).
Les Yay: The possessed Mary Marvel keeps coming on to Supergirl the more they fight, with Mary showing signs of being a Combat Sadomasochist.
Moral Event Horizon: Inertia crossed it (again) when he killed Weather Wizard's baby son. Also Libra and Human Flame, for killing Martian Manhunter. Darkseid obviously crossed it long, long ago, but what he does in this story is certainly up there with the worst stuff he ever did.
Nightmare Fuel: The new nature of Darkseid, not to mention Mandrakk. Darkseid has transcended his physical form and become a nightmarish Eldritch Abomination who's pulling reality down into the abyss, and Mandrakk is an interdimensional vampire feeding on the death of reality. Who's heavily implied to be the original Monitor.
The release of the Anti-Life Equation, which is released on EVERY form of electronic device: TV, Internet, radio, PDA, Cellphone, GPS, etc. The book proclaims that over a billion people are enslaved this way with the initial release of the Anti-Life Equation, effectively giving Darkseid control over Earth and forcing the unaffected heroes of Earth into hiding for the second half of the storyline.
New Media Are Evil: La Résistance publishes special editions of the Daily Planet to communicate. For some reason, Darkseid doesn't bother to have the Anti-Life Equation put on posters or anything while he has Justifier slaves burning books...
What an Idiot: At the end of Legion of Three Worlds, Superboy-Prime manages to break reality (again) and doom himself to being an unpowered kid in a world where everyone hates and fears him by punching out the Time Trapper who is his own future self.