Stillanerd you make a very compelling case for Carlie. Unfortunately, the character is just so "meh" (I don't HATE her, I honestly just don't give her much thought at all) that IF she is revealed to be Kindred, I would be completely underwhelmed.
"The White Queen welcomes you, TO DIE!"
That's why I find the "it's not who but why" hook to be the bigger more interesting question. I think with all the One More Day hints in this run so far anything not relating to One More Day would be a disappointment. The hints have been seeded and it's pretty much the biggest Spidey stones you could have to try and address it.
Kindred being from hell, the Mysterio being confirmed to have been dead and in hell rather than just saying "master of illusion!", the To Have and To Hold callback literally being the first page of this run, the hints that everything feels right being with MJ again but still like something's missing, Peter thinking of proposing again but Kindred trying to keep MJ away from him, there was also a direct line in there somewhere about there being one big thing he can't remember. It's past the point of simple teases, it feels like it's building to something big and it doesn't get much bigger than that. I don't know how they even do it because it's still a touchy subject but trying to go into difficult territory like that is more interesting than playing it safe.
There are several additional factors pointing to the end of OMD. 1: Spencer has been fixing problems with Amazing ( Kraven being one example). 2: Mephisto being dead. 3: The rise of Miles so the need ( or perceived need) for Peter to be sacrificed for Spider-Man is no longer there.
Brian Dewolff Jeans brother and original Wraith. I went into more detail on the Kindred? Thread. Fits alot of the parameters
I think using Sin-Eater can serve two purposes - first to remind Spidey how he failed to recognize Stan Carter had apparently changed after his treatment and didn't help him integrate back into society, second, Kindred could also have something planned for Sin Eater himself to avenge Jean's death. As for hating Pete, I think having the ability to read Pete's mind and seeing how Pete believe he failed so many times to save people, Uncle Ben, Gwen, Captain Stacey and maybe even Jean, he wants revenge on Pete more than Spidey. Like I said in my other threat, I think the worst thing Kindred can do is force Pete to kill MJ or Aunt May as revenge for Jean's death.
But this is all is hypothetical
There are so many characters affected by different variables that fit the profile. What about the woman Peter punched in Spider-Man Versus Wolverine? Or how about Jessica Carradine? It would be interesting to bring her back considering she is the Burglars daughter. She isn't dead though and she did make peace with Ben Reilly before disappearing. Then you have Jackpot who died because of a mistake Peter made on top of her mutant growth hormone use. There are too many people that could hold a grudge. Truth be told at this point the only way I'd be satisfied is if was the burglar or even Ezekiel based on the line about not liking killing innocent people.
I've been enjoying the slow burn on Kindred (more or less), but the "not who buy why" really bothers me a bit. Not that I'm tied to a specific person (or Kindred even being from the short list of guesses), but it seems to me that the why has to be inextricably be related to the who for the story to really land. Like, if it's Nathan Lubensky's long lost son who happened to have been killed during a Spidey/Doc Ock fight (this is definitely not a prediction), then the why is important but the reveal is so boring that the momentum of the story is just killed*. If 'why not who' is more in the vein of "It's Harry, and the real mystery is who is the guy that's been running around since BND" that could be interesting, but I still feel the 'who' will be the reveal we're talking about more than anything else.
I should say, I'm definitely in the "this is not a OMD-related story" camp at this point**, so the why also doesn't have any import for me yet. I'm doing my best not to project my opinions or hopes onto the story because I'll inevitably be disappointed if I'm too invested in a particular outcome (you get burned by Star Wars too many times and you finally change your MO). That doesn't stop the mindless speculation and discussion, but just my general investment in my rightness
*The story will obviously continue on (it's already written and probably being drawn as we write), but fandom (me among them, probably) will start picking apart the process elements of the story if the reveal is boring - what was so special about this nobody that they got to rise up, do all the clues and hints Spencer left work, is this Hail Hydra all over?, etc.
**That is, given what I've read until now, I do not think Kindred is a result of or pissed off by Peter's deal with Mephisto for reasons both in and out of universe. That is obviously not to say that I know anything, so Spencer might be writing the much sought after OMD sequel, but I just don't think it's happening now.
Blue text denotes sarcasm
My hypothetical is Sin Eater being used to punish Peter over Jean is not accurate. Why? The punish Peter over someone being cured was done before and more then once, most famously with Norman Osborn and Gwen eventually dying as a result. But, guess what, Peter is not Christ he cannot save everyone, and I hate him punished over and over again. As for someone dying I could see it being Aunt May. That would shock the readers. Personally speaking They have done so many Aunt May in peril stories it is not funny ( think back to last year’s Cancer). I have become numb to these stories ( ASM 33 excluded), and would not be sorry for her to go ( maybe letting Peter know she is aware he is Spider-Man and to let her go to Heaven with Uncle Ben).
I have become numb to the deaths in the Spider-Man portion of the universe. When Harry died, it had a lot of impact. Aunt's May's death in 400 was very well written story. Then these characters come back and shrug everything off. Gwen Stacy may be dead, but we have had near infinite numbers of clones of hers that i couldn't even care less if Kindred turns out to be the original Gwen - i blame Sins Past for making me dislike her greatly to the point where i don't even want to see her again. But senseless death's for shock are the spider-man cliche now. It's boring.