I have GOT to add on to this cause I am sick of people dunking on disabled/chronic pain headcanons for shadow.
1. The title of "Ultimate Lifeform" doesn't mean anything, it was a label that was put on him by an overzealous creator who had a lot of bias over his own creation. Its a title that often brings Shadow stress and pressure and he's quicker to perceive Sonic as the true ultimate lifeform rather than himself when he's being honest. Saying he can't be disabled or have chronic pain because he's "the ultimate lifeform" doesn't really mean anything.
2. In Gerald's diary, which was given as a booklet alongside sonic x shadow generation pre-orders (which I own), it's mentioned that Maria designed Shadow's jet boots to help him get around. To me, this implied that he had to have been struggling in getting around for Maria to feel the need to give him some form of aid, perhaps even a mobility aid. She would be the only person on the ARK who would notice and understand someone else's struggle with their own body.
3. Even if he doesn't need the jet boots, HE NEEDS his inhibitor rings. It's not stated very clearly but it's implied that he would suffer in some form or fashion if he lost them- that his own power would overwhelm his body and damage it. As someone with an autoimmune disorder where my own body overproduces white blood cells and overworks itself and ends up damaging my own body by overwhelming it, that makes me feel like Shadow's inhibitor rings are a lot like immuno suppressants, a medicine that people with immune system related diseases use to suppress or inhibit their own immune system and prevent it from damaging themselves. If shadow needs his inhibitor rings to stop his body from damaging itself, then that's a disability where he's utilizing an aid to live, or live on the same level as his peers.
4. In sonic x shadow generations, shadow says that his doom powers are from his alien DNA and are a part of his body. However, when he uses them, he appears to be in visceral pain. He screams out and grips at his face and body and keels over in pain. If those powers are from his own DNA and body, and are hurting him, and is something that can reoccur, then it counts as chronic pain or a chronic condition!! It shouldn't hurt to use your own body, but it does for him.
5. Shadow is a PROTOTYPE. He is only the second prototype, and the new manga confirms that he was a FAILED prototype. He was made to cure maria but in the manga it was confirmed that it failed and he never could have cured NIDs. The first prototype, the biolizard, literally needed massive, invasive life support machinery to live at all. Think about how imperfect the prototype right after that one might be. The Robotnik family seems quick to claim that rushed or unfinished projects are "perfect and ready to go," that's kind of how all of eggman's plans fail (as we've learned from Starline in the IDW comics) so I feel like Gerald may also be claiming that his creation, Shadow, is perfect, even when he isn't even able to solve the problem he was made for.
6. Shadow seems to fall out of his super form faster than Sonic and faint when pushing himself to remain in the form (he faints a lot in general, compared to other characters (some examples being Sonic Adventure 2, Sonic Prime, and Sonic Battle which turned into a multi-day coma under Rouge's care). He also seems to generally avoid going super compared to Sonic. I'm not sure how natural going super is but it seems almost easy for Sonic and Silver. Even when Sonic runs out of time in his super form, he never faints from it (which is made evident from the sonic advance games where his super form runs out while rescuing Vanilla from falling, but he's still fine and smiling & continues to carry someone larger than him with no struggle right after losing his super form).
7. I would honestly also count memory loss as a potential disability or chronic condition for him. He usually recovers his memory but it is genuinely a reoccurring problem in canon for him to lose memories or have his mind temporarily wiped/controlled/brainwashed.
8. PTSD can be considered a disability if it is detrimental enough to someone's day to day life. In America it can be legally considered as a disability and people suffering can be given aid under certain terms. In the comics, games, and official animations, Shadow's flashbacks of Maria's scenes are extremely consistent, invasive, uncontrollable, and sometimes detrimental to him. Uncontrollable and repetitive flashbacks of the traumatic scene accompanied by panic attacks are symptoms of PTSD, and I don't think it's subtle that the writers are really trying to convey this trait for Shadow.
Being disabled doesn't necessarily mean being super weak. He uses aids and tools to do what he does but he still does it well. It's not "inaccurate to canon" for disabled & chronically ill people to relate to him and it shouldn't be insulting to say his chaos energy & black arms DNA is similar to disabilities and chronic illnesses.
