* CopyCatSue: Shinjiro, especially in the first Shadowchasers fic where he was quite clearly the author's version of Yusei Fuso, right up with giving him a similar deck to Yusei's and a DarkAndTroubledPast with Yusei and even having an undefeated streak in the first fanfic, something the author was criticized over. Fortunately this was toned down in ''Power Primordial'' wherein he changes his deck and actually loses an important duel.
* HilariousInHindsight: The cards that Bruno uses in ''Tournament of Shadows'' are based on characters from ''Literature/AlicesAdventuresInWonderland'' with a much DarkerAndEdgier theme, including an older version of Alice using a Vorpal Blade as a weapon. The author first introduced these cards in a fic called ''Legacy of the Duelist'', which appeared ''years'' before [[VideoGame/AmericanMcGeesAlice a certain video game with similar themes]], was released.
* MoralEventHorizon: Several examples:
** [=DaPen's=] brutal MindRape of both Jinx and Gears in the first fic, along with the rather [[FateWorseThanDeath horrid description of his plans for them]] qualifies.
** The Aboleth from the second fic crossed this line a long time ago. It was willing to murder the populations of entire planets for no reason other than greed. It did so at least once, with the homeworld of the Primordial Titans, and tried to do so on at least one other occasion.
** In ''Torment'' Lorelei crosses it by her rather sadistic act of CruelMercy, turning Nichole into a cat after forcing her to try to win an antidote back from her (intending to keep her as a pet once the change becomes irreversible).
** Lareth damns himself by [[spoiler: turning on his partners, shooting them in cold blood in order to flee and save his own skin.]] Clearly, what ultimately happens to him is not undeserved.
** In ''Backwater'', Solex's in-story crossing is done when he and his entourage beat and gang-rape Kastleneid (his golem servant, purchased for the intent of serving as a SexSlave) and leaving her to die in a gutter like trash, for no other reason than to blow off steam following his public loss to Tsuki. Clearly, when a demon and a vampire are both sickened by your actions, it's clear you've gone too far.
* UnfortunateImplications: 7th Librarian changed Tsukihime's name to Tsuki via RetCon after research showed that it is inappropriate in Japanese culture to name a child after a deity.