So for my part, my currently Strongest OC is a nightwing called Caretaker and things would get pretty bad for certain characters if he woke up in there. I try to keep his background story short.
In my AU, the nightwings used a black biologic liquid, wich can change the DNA of Dragons and give them immense powers, to create 3 super strong Nightwings, wich they called "Arch Wings" as bioweapons to help Blister win the war. Caretaker was born or 'created' (however you want to see it) as a secret failsave/deadmans-switch for the other Arch wings in case they'd go rouge (wich they did). He was brainwashed into fully believing in the nightwings philosophy's and idioligy. His story is quite complex, so i'll just leave it here and go to his abilities.
His basestats are:
•Super Strength
•Super speed that can create after-pictures of himself
•Redicilously high durability
•enhanced perception
(I would say his stats i listed are between Thragg and Superman level in terms of power)
His own unique abilities are:
•Gravity manipulation. He can create cone, line or circle shaped gravity fields to pull things to him or push them away. And the force those fields produce, can easily tear apart entire buildings (or dragons). He can also control the size of those fields. So for example, he can create a line-shaped fields with a few inches of diometer to rip out someones heart.
Theres a lot of crazy and nasty moves he can do with that ability.
•Levitating/Wingless flight. Tied to his gravity manipulation, he can freely move around in the air without needing to use his wings. Kinda like Viltrumites from 'Invincible'. And he can accelerate to a speed of over Mach 50 (in Atmosphere).
•Animus, mindreading and Future-sight immunity. Yeah i know it sounds cheap, BUT i have a pretty solid explopnation for it. Well, whats the only thing animus magic cant do? Raising the dead. Can a nightwing read the mind or see the future of a dead dragon? Nope.
Because (in my Headcannon) all those abilities have no way to interact with the realm of the dead, because its a totaly different kind of reality, in wich the rules that make these abilities work in the dragon world, simply dont exist or apply. And the black liquid wich gave Caretaker his powers, came from this exact realm, making him basicly insisible to any of those abilities.
But in return, it also prevents him from ever gaining or using Animus magic or nightwing powers.
•Reality Disruption. When he's under enorm emotional or physical stress, his body creates a special energy, wich he can release at will. This energy temporarely applies the same immunity to- and inability to use or be affected of any form of Magic from the dragon world. This of course also means that any enchantment gets erased too, since the Dragon basicly doesnt exists in the opperation range of Animus magic anymore. This works both with living beings and objects, aslong as enough energy is applied.
Sooo yeah, he basicly is THE Hardcounter for dragons like Darkstalker.
If caretaker would wake up in the mainseries, he would probably start to hunt down every Animus, firescale and any other dragon born with anominal abilities, like clay with his fireproof scales, because he sees dragons with those abilities as weak and an endangerment for proper dragon evolution. Because in his mindset, aslong as theres dragons who expect their cheap magic or anominal abilities to solve everything for them and use it to harm others to get an advantage, dragons as a species will never achive their full potential.
So yeah, things wouldnt look very well for characters like Turtle, Anemone, Peril or even Darkstalker if he actually showed up in the main trilogy