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.
Complete Monster: The evil, power-hungry Barago was once a member of the Makai Knights who are dedicated to defend humanity from the demonic Horrors. Nearly every horrible thing in the series can be traced back to Barago. He made the innocent heroine of the series into a vessel for a demonic being known as Messiah, which would allow Messiah to consume both the girl and then the world (for nothing more than his personal gain). He murdered series hero Kouga's father, and The Lancer Rei's family to manipulate them further in the future. To prove he has no attachment to humanity or human beings, Barago cuts down a mirage of his own mother to prove that his family means less to him than power. Barago is willing to allow humanity be devoured for his own gain, and carelessly uses and discards whoever is in his way. When one hero begs Barago to remember why he once joined the order of the Makai Knights, Barago's only response is to coldly say he can't even remember.
Ensemble Darkhorse: Zaruba. From his Deadpan Snarker attitude, to being a genuinely funny guy, to being something that doesn't scream Stop Helping Me!, the little sentient ring became very well liked. To the point where he even is at the beginning of many episodes and he technically gets resurrected after his first 'death'.
Evil Is Sexy: Kaoru stops being annoying and starts being slightly attractive when Messiah possesses her.
Heartwarming Moments: The end of the Beast of the White Night special is filled with this. There's Rin using her magic to create butterflies so she can make her brother, Tsubasa, smiles, which he did. There's also Kouga seeing the spirit of his parents happily together and very proud of their son, after which Kouga bow to them in respect. And the final scene, with Kouga coming home to find Kaoru there, finally reuniting with her.
Les Yay: Agi and Magi in Tougen no Fue and Jabi and Rekka in the end of the movie.
Invoked in KIBA Gaiden. Barago's Face-Heel Turn is only considered complete after he kills an illusion of his deceased mother.
Nightmare Fuel: The whole damn thing, from the monsters and the Hero costume designs to the freaky intro and the dark settings. One of the most notable HAS to be the Clown Horror.
Ship Tease: Rei and Kaoru's relationship in the first series is a rather twisted version of this with Rei alternating between flirting with, threatening, and protecting Kaoru. Rei's Madou ring even states in GARO: Gaiden that Rei was at some point attracted to Kaoru. Of course, it could be considered well and truly sunk after he nearly forces himself on her. But since the first season, they have become rather good friends and in episode 12 of Makai Senki in the Couch Gag end credits, he leaves a bag of sweets outside her window.
Tear Jerker: The old couple's story in Makai Senki episode 6.
Episode 15 of Makai Senki. Flashback during Kouga and his friends' training with Wataru Shijima. Everything seems to be going well, with Kouga and his friends forming a strong bond of friendship and Wataru being proud of their ability, until the last minute where a Horror comes to the village where the training is being held and kills all of Kouga's friend, while he could only watch as it devours them. It makes Kouga killing the Horror in the present time much more satisfying.
Visual Effects of Awesome: Soukoku no Maryu is a visual feast throughout the entire movie, justify by the increased budget for it. Special mention goes to the climax, especially the fight against the Maryu.