General: Post-amnesia intuition to trust the wrong person. Details
General: A missing person is found a heartbreaking state in a place where they're simultaneously least and most expected to be. Details
General: The classic dynamic of messy histories colliding with the present. Details
General: The cynical nonhuman falls in love with humanity through interactions with one ordinary human. Details
General: The dynamic of a devotion so intense, it becomes self-destructive. Details
Alu (FAITH/Undertale): Alu meeting Undertale's Toriel and forming a tentative, semi-amicable relationship with her through their mutual desire to protect small children. More info.
Alu (FAITH/KDPH): KPDH Verse Alu interacting with Rumi under the guise of being an "imaginary friend" or uncle on her late mother's side, when in reality he is actually a close friend of her late mother, or her father. Details
How to Train Your Dragon: Any of the dragons forming a deep, strong bond with someone only to be taken from them via mind control or by poisoning and only snapping out of it thanks to their bond with said person.
Mr. X / Nemesis (Resident Evil): Nemesis/Mr. X (or both) being recovered by a different organization and working under them.
Nemesis (Resident Evil): Nemesis forming a bond with someone, mutating to the point of going totally feral, and their bonded person being the only who can help him calm down.
Nemesis (Resident Evil): Nemesis trusting someone enough to show them the device in his head that allows Umbrella to direct him and asking them to remove it so he can focus on being there for them and not constantly having to think about mission work.
Nimona: Sonic Cinematic Universe Nimona being another being discovered, captured, and molded to become a perfect bio-weapon just like Shadow and leaning into the villain role after being betrayed. Details
Rayn Wilder (OC / Puss in Boots): Rayn interacting with Death (Puss in Boots: The Last Wish). Her having struck a deal with him while bleeding out after an investigation gone really wrong to spare her and help her until she can solve her lifelong case and avenge her partner's death, and in exchange, he can take her life when she's finished. More info.
Six the Intruder (Mandela Catalogue): AU where the alternates are actually just weird guardian angels trying to protect humans from threats with varying degrees of success because of how terrifying they tend to be.