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: G-Senjou no Maou
Complete Monster: Maou, the Big Bad, whose total disregard for human lives puts him way beyond the Moral Event Horizon. wants revenge on Usami and Gonzou for ruining his family´s economy (leading Maou's father killing Usami and being sent to jail) and for putting his mother and brother in massive debt respectively. During the process, he kills Haru's mother, who had nothing to do with that situation under the guise of a terrorist attack. Later, he takes a whole city hostage, incites a massive riot which claims lots of innocent lives, just for his father to be released from jail. Ironically, the poor father only enjoyed his freedom for a couple of hours before succumbing to a heart attack. Then, he tries to kill Haru herself after his defeat.
Kyousuke's former "landlord", Kanu, a violent abusive drunk who messed up Kyousuke´s life.
Diabolus ex Machina: This troper felt that the Haru epilogue had shades of this along a sudden grab of the Idiot Ball when he allows himself to be arrested and then convinces all his friends that he feels nothing for them in order to salvage Haru's reputation; after all, revealing the fact that 'Maou' had killed Haru's mother in front of her would definitely make a strong case for her mental state while chasing him down, and telling the investigator that he had acted in order to stop her from becoming a murderer would have definitely made him look less villainous to the media. He would have no doubt served time, but the ending would have been alot less of a needless Tearjerker.
Moral Event Horizon: When you learn that Maou used a terrorist attack in Russia as a convenient way of killing Kaoru Mishima, Haru's mother, simply because she is the wife of the person who ruined his father's life, you will despise him, if you have not already done so when he kidnaps Tsubaki's kid brother, Hiroaki, then proceeds to corrupt the poor girl.
Villain Decay: Mephistopheles/Saijou in chapter three initially comes off as a cold but honorable right-wing extremist, later he is revealed to be more of a sociopath who is easily manipulated and controlled.