Eugene emerged as the unlikely hero in Rick’s war with Negan in the season eight finale of The Walking Dead. Just as it seemed Eugene was fully committed to being Negan’s bullet maker, never again to use his mental fortitude in service of Alexandria, the Kingdom, or the Hilltop, it turned out he was playing the long con. Rick and the gang fell right into Negan’s trap, finding themselves surrounded by heavily armed Saviors. When Negan gave the order to fire, all of the guns backfired, either killing or injuring most of the Saviors.
After a fairly short fight the Saviors surrendered, and Rick and Negan had what may be their final showdown. It looked like Rick was going to lose but he caught Negan off guard by saying that neither of them had to die, just like Carl wanted. But then Rick slashed Negan’s throat. Negan didn’t die though and Rick told Siddiq to save him, much to the chagrin of Maggie who had to be held back by Michonne.
Maggie’s anger over Rick letting Negan live will likely play out in season nine. At the end, Maggie is talking to Jesus about Rick being right to let the Saviors live, but not Negan. Maggie says they need to build up the Hilltop better than it was before. They need to build up their strength so the Hilltop can defend itself. Then the conversation turned ominous when she said, “But Rick and Michonne... Rick was wrong to do what he did. Michonne, too. So we're gonna bide our time, wait for our moment... And then we're gonna show him.” And Daryl emerged from the shadows saying, “Yeah. We will.”