Something I find interesting about Shadow’s movie design is how he seems to be lacking his inhibitor rings.
He very much could still have them as it’s hard to tell or not but I like the idea of Robotnik or Agent Stone putting them on him after they witnesses his power or something.
Mainly because it would be cool if we seen abit of that power but got to see the full thing near the end of the film maybe after Robotnik is out in danger, always liked the relationship between the two with Shadow having having strong level of respect for him because of his blood ties to his creator.
Don’t think Shadow will become a good guy in the end because we’ve already done that with Knuckles but maybe rather being slightly swayed into being one or dying fighting against a bigger threat like Chaos or Metal Sonic.
Choose those two because they both could show a level of pain and chaos that ties back into Shadow.
That’s not to say Biolizard couldn’t work, it’s a unstable mess that’s driven on revenge and following orders but I personally would really like to see how Shadow would react to Chaos’ similar pain and loss and Metal’s lack of identity with the desire to become the real Sonic so bad that he becomes the very antithesis.
One so blinded by pain that it would inadvertently kill those similar to the ones it lost and one so driven by purpose that it would end up losing it just to reach it.
Also with the inhibitor rings I feel like those were added in the game’s canon to stop Shadow from becoming like the Biolizard so I don’t know how that would work out if he didn’t have them at the start, maybe could be hinting at him being unfinished and therefore not really the ultimate life form.
Anyways that’s enough of me spitballing ideas, really hope if Chaos or Metal don’t show up in the film then either of them will be the baddie for the Knuckles series, if only because they have pretty great villain stories.