Here is why I think it's Carl that got killed by Negan.
Notice how all the saviours are adults. No kids or teenagers, he wants these people to work for him so if theyre's no kids then why would he want him, this is one reason I think it's Carl. Another one is the shadow is on Ricks left meaning it's between Sasha, Aaron, Carl, Eugene. Kirkman said beloved I don't mind Aaron & Eugene but they aren't beloved. Sasha is just going to be that annoying survivor meaning Carl. Another one is a few episodes back at the hilltop they said they killed a 16 year old boy just to make an impression. Negan is also impressed that the victim got back up after one hit. You wouldn't expect that from a kid now wouldn't ya. The scene with Enid & Carl is foreshadowing it aswell with the " what if you never come back " quote by Enid. Plus
Lauren Cohan, Michael Cudlitz. We're both fuming with the script over how shocking the scene is. Beating a kid to death is pretty shocking.