For me it's characters who are either name-checks or re-invented to the point they are nearly unrecognizable.
Was there any reason for the character in Iron Man 3 to be named Mandarin besides it being the name of a classic Iron Man foe? I sort of get the argument that the
real Mandarin wasn't Ben Kingsley but Aldrich Killian, but even Killian was too different from the classic Mandarin to seem like it was anything more than using the name of an Iron Man villain without really wanting to use that villain.
The same with Zemo in CA:Civil War. Loved the motivation and the role the character played ... just wish the guy wasn't supposed to be the movie version of Baron Zemo.
And in the DC movies I'm left scratching my head wondering when Jonathan Kent became an impediment rather than an inspiration for Superman. Or how the Joker managed to disguise himself as Lex Luthor in Dawn of Justice. (
Wait, you mean that his seeming random dialogue was supposed to make him seem a genius and not an obvious sociopath )
My personal favorite though is the Atom on
Arrow who manages to be nothing like the Atom for much of his early appearances because they just pasted the name Ray Palmer on a character designed to be Ted Kord (the Blue Beetle). And Palmer's fiancé wound up with a name change because they had already introduced her character (Jean Loring) in a different role.