Iirc Glen and Dale were close in a father son sort of way.If we're going that way in thinking I'd still say Glen. He's the only one that hasn't lost anyone close. Hershel is as close as it gets and that was what, two seasons ago? If they were showing all that to set Abraham up it wouldn't make sense to kill him without showing the same stuff with Sasha which they didn't. Sasha would make more sense to fuck with Abraham, but Negan's big thing in the comics is that he doesn't kill women.
Rick just lost porch dick's wife, Sasha lost Bob last season and her brother before that, Maggie lost her sister and Hershel in the last two seasons, Daryl lost Merle and then Maggie's sister. Glen hasn't lost anyone that was closer to him than to anyone else in the group since the beginning. No one from Abraham's initial group has died either though. But, like others have said he's more likely to kill someone weak if not Rick and Abraham stared him down the whole time. That pretty much leaves Eugene and from Negan's perspective, Glen since he cried the whole time and Maggie made it obvious that Maggie was a weakness to him.