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.
Kachess' reaction to Yufina going missing is to search almost every country to find any form of evidence as to were she went, then disguise himself as a woman to sneak into the Duke's harem and kill the guy to save her. Talk about dedication!
Hell Is That Noise: The guillotine sound in Daughter of Evil and Servant of Evil, except in certain versions where it just sounds like a rope being cut, and other versions where it's left out entirely.
Les Yay: After some years, fan speculation over whom Michaela truly loved - ranging from her having a true relationship with Kyle, as is implied by quite a bit of fanart, or actually being in love with Allen the whole time, which was input into its fanmade song - eventually ended up moot because regardless of whatever she felt towards Kyle, her true love was towards Clarith.
Also occurs in the songs where there are twoRins. In South North Story Rin and Riliane get very intimate with each other and in Screws, Gears and Pride the two Rins pretty much give each other the "it's not you, it's me" speech when they part ways.
In the trailer for Praeludium of Red, there's a brief image of Elluka and Gumilia looking awfully chummy...
Some translations of Capriccio Farce have the doll call Ma "my dear Sorceress of Time".
The Madness of Duke Venomania Manga adaptation makes Lukana Octo a walking magnet of these. She was good friends with Lilien Tanner (a baker), and bought her a beautiful bracelet to match hers. In fact, looking for Lukana is Lilien's motivation to follow the duke at first. There's also an scene where Lukana is hugging and talking to Mikulia about the duke/their situation. Mikulia's only answer is that she loves Venomania... and she also loves Lukana.
Irina deserves special mention here, after all she is pretty much the one manipulating EVERY single character (Not even Elluka of all people saves herself from this ...literally) behind the events of Story of Evil and the Pere Noel Organization, we could fill an entire article just listing each one of her schemes, including manipulating Prim Marlon the former resident Magnificent Bastard
MA, too. She KILLED GALLERIAN'S ENTIRE FAMILY because he didn't want to work with her. Not to mention, she seems to be manipulating the hell out of The Clockwork Doll, too...
Magnum Opus: Story of Evil. Servant of Evil in particular. It's the song that gained mothy his producer name in the Vocaloid fanbase, after all.
Memetic Mutation: After Story of Evil's supplementary material was released, fans are prone to making comments that go "CURSE YOU PRIMMARLON!"
Before that, there was "IT'S ALL KAITO'S FAULT!" due to the fact that whenever something went wrong in the Seven Deadly Sins series, a character played by Kaito would almost always be the cause of it.
Misaimed Fandom: The Duke from The Madness of Duke Venomania seems to have quite a large fanbase, if the YouTube comments for the song are anything to go by.
Allen in Story of Evil and Kayo in Tailor Shop on Enbizaka get a bit of this too.
Moral Event Horizon: Every Deadly Sin character crosses this except Rilianne, who was not yet beyond redemption:
Tear Jerker: Many, but special mention goes to Servant of Evil, Regret Message, Daughter of White, Girl of a Miniature Garden, Flames of Yellow Phosphorus, The Last Revolver, Maiden of Wood ~1000-Year Wiegenlied~, Kept Waiting for a Response and White Brick and Black Mourning Dress.
A minor one where Germaine found out that the princess she captured in the Lucifenia Revolution is actually her foster brother whom practically grew up with and loved like family.
Doll: How can the lifeless me understand? How can the heartless me understand?
Meta Salmhofer, in Escape of Salmhofer the Witch. Growing up without parents and engaging in a life of crime for a while, she had a change of heart after giving birth to twins, and resolved to protect her children from experimentation, only to get murdered and her children kidnapped by someone who'd gotten Meta arrested for something she didn't do previously.
Woobie, Destroyer of Worlds: Margarita from Gift From Princess Sleep-Bringer. She was basically broken from the start, made into a Stepford Smiler who felt like everyone would be better off dead since they were all so unhappy in her eyes. Rin of Flames of Yellow Phosphorus also counts, as she committed that crime because she had been denied food and shelter by her father.