First of all, i know TWD is known for being tragic, everyone you ever liked will die somehow, i didnt watch the tv show much but i read the comic allot. It was not only sad deaths but also incredible fights, bloodrages and imposible situations(Tyreese in the gym)
I'd go with Cristha and Omid but i got a hunch.. i feel like those two are Kenny and Lilly/Molly, yeah pretty imposible but it makes kind of sense.
1- The epilogue, that got to be chapter 10 or 12.
2- Clementine DID find Cristha and Omid and they travelled away from Crawford.
3-But they are ambushed by Walkers or Bandits and they sacrificed themselves to save Clem or they got separated or they where killed and Clem ran off or something else.
3- After all that shit happens, Clem is alone wandering that wasteland, already far away from Crawford.
Those two some how turn out to be Lilly/Molly and somebody else.. Kenny?
Why Kenny? Because if he survived rescuing Cristha/Ben, he didnt know where to go, Lee didn't told him the plan(whichever you choosed). He will most likely wander around and be found by Molly. They tried to find the other guys and they did it, they found Lee(Zombified/weak/dead/immune).
If we compare Chuck situation with Kenny's, Chuck was older but he was brave and skilled, he survived alone for so long, he knew his way around the walkers that's for sure, perhaps he got no more strength to keep fighting, perhaps that faggot Stranger set him a trap.
Now when Clem shooted Lee, i'm sure i heard a moan wich could mean:
a- Clem missed the shot and get the fuck out because he couldn't do it.
b- Lee turned already OR he passed out again.
Lets do a little flashback:
I dont think Lee would survive like the guy from the comic who got his leg cutted in the prision(it was the husband of the blonde old woman with short hair) or like Herschel in the series. Because he waited too long, Lee was really messed up.
Remember the Mechanic guy from the comic? He got bitten but he didn't die in what? 3 days? Then they left him near the city because he "wanted to be with his family"(who died in the city). His body was really fighting that virus, maybe Lee's body too but he is way weaker.
Even more, we don't know if he died, when they left him, he was very weak but not dead, perhaps he was inmune.
Now back to Kenny/Lilly.
Lilly went in the RV, it was broken, she went as much as she could and then came back perhaps on foot perhaps in a bicycle, maybe Cristha/Omid and Clem or Kenny/Molly took the train and found her following the tracks and gave her a ride.
Now that's all i can think off, yesterday when all this shit came to my mind it make so much more sense but i forgot most of it, i'll give it more tough.
I'm sure of one thing tough, Lee is dead or will die, an immune survivors is not something good for the story(it will for the comic that it was getting pretty boring last time i readed it, around issue 65-70 i think),