Broken Base: Good God, it's tempting to say everything about this fic, but really, let's just say trying to meld My Little Pony: Friendship Is Magic and Death Note was a weird choice would be understating the fact. Some major points though; Twilight as LightYagami! Twilight murdering two of her best friends! Fluttershy acting as a second Kira and killing Sweetie Belle! The Apples acting as a third Kira!...
Catharsis Factor: Given some of Twilight's more reprehensible actions, it's very satisfying whenever L knocks her down a peg.
Crazy Is Cool: Pinkie Pie is just as much of a Cloud Cuckoolander as her canon self, and her scenes are some of the most fun to read in the story.
L is an Emotionless Girl and her social awkwardness is played up compared to the canon L, but her scenes are an absolute blast. Byuk is also just as creepy as Ryuk but brings a lot of comic relief, and it's very cathartic when he tells Twilight off for killing Pinkie Pie in order to get onto L's team.
Bon Bon's reveal as a changeling in Chapter 31 is pure awesome. She almost gets to take out Twilight and avenge L's death, but sadly Twilight had planned for that.
Pinkie Pie. She gets killed a third of the way into the story, but makes a significant impact in that time, and seems to have put a Thanatos Gambit in place to take down Kira.
Sweetie Belle only has a few scenes before dying in Chapter 14, but the wayshe goes out makes it one of the story's most memorable moments.
For many, Twilight crossed it when she killed Ray and the other EBI agents, thus going from only killing criminals to targeting anyone who opposes her. And if not then, she crossed it when she engineered Rarity and Pinkie Pie's deaths in order to gain enough sympathy to infiltrate the L team.
Second Kira crosses it when she kills Sweetie Belle. Even Twilight, who still has some delusions of being the good guy, is disgusted by this.
Mer killing Granny Smith in order to force the Apples to be the Third Kira. Which may or may not have been on Twilight's orders, in which case this is on her, too.
It's actually implied that Twilight set her death up ahead of time, and Mer was just acting like she was the one doing it. If that were the case, then she crosses it when she writes Spike's name on the Death Note and makes Twilight kill him right after Sunny Days dies.
Narm: It's Death Note with ponies. Even if you're a fan of FiM, it can still be hard to take seriously. Especially when the characters start acting wildly out of character, like with Twilight murdering Rarity and Pinkie Pie.
Tear Jerker: Several, particularly the funeral scene.
Now tied with Ditzy/Derpy learning about her fiancee's death.
Sweetie Belle's death counts, too.
Anyone familiar with the original story knows what's coming, but the outcome of Twilight's Gambit Roulette still hits hard.
