Shang-Chi: 8 Characters Who Should Appear
1. Trevor Slattery
As I discussed at the outset of this list, Iron Man 3's version of the Mandarin was so divisive because the Aldrich Killian reveal felt deflating, though it was no fault of Ben Kingsley and his portrayal of Trevor Slattery. Trevor was a great, entertaining character, but the twist that the Mandarin wasn't real stung a bit simply because Kingsley was just so good as the seeming terrorist leader.
It's been over six years, though, and Marvel at least course-corrected the Mandarin character early enough that we're now on the road to getting a proper interpretation. That said, though the "All Hail the King" One-Shot set up the real Mandarin's existence, Shang-Chi and the Legend of the Ten Rings is going to have to address that situation in some way for the larger audience that never saw that short film.
Last we saw Trevor, Jackson Norriss had broken him out of prison to face the wrath of the Mandarin. It's easy to assume that the Mandarin simply killed Trevor immediately, but it's hard not to hold out hope that we see Trevor again all these years later, perhaps imprisoned by or indentured to the Ten Rings. Not only would his appearance easily help explain the Mandarin situation to the wide audience, it'd give us the opportunity to see more of the scene-stealing Kingsley and maybe even give Trevor more dimension and redemption in the process.