Warning! SPOILERS for The Walking Dead season 10 episode 12 ahead.
Beta, and it's her death that may have just sealed Beta's fate.
The back half of The Walking Dead season 10 has seen the baby abandoned by the Whisperers in season 9. Mary chose to leave the Whisperers thanks to her budding friendship with Aaron, and her defection has been one of the few hopeful developments this season. Now that she's dead, though, her death may well lead Aaron to seek revenge.
In The Walking Dead season 10, episode 12, "Walk With Us", the survivors are scattered following the Whisperers' attack on Hilltop. One group includes Alden, Kelly, Mary, and the baby, Adam. They get surrounded by walkers and fight off as many as they can, but soon spy a nearby van where Alden and Kelly seek shelter with Adam. Mary, however, chooses to remain outside and lead away the walkers. She successfully kills the pursuing walkers, but just as she finishes, Beta arrives and disembowels her. He plans on waiting for her to die and turn, but before she can him as fresh walker, Alden shoots in the head with an arrow. Beta then runs off, but his decision to kill Mary may signal his own death is soon to come - and at Aaron's hands.
In kill Jesus, he's shot in the chest with an arrow by Aaron and killed.
Now, AMC's The Walking Dead isn't able to directly adapt how Beta dies in the comics, but in having it be him who kills Mary, the show has created a situation in where it's now even more likely to be Aaron who kills Beta. On the show, Mary and Aaron have become friends since the former was first sent to spy on latter. Through their meetings, Aaron was able to earn her trust and eventually convince Gamma to abandon the Whisperers and become Mary again. Once Aaron learns she's dead and that is was Beta who killed her, it's very plausible Aaron will make it his new mission to kill Beta. The Walking Dead may have been building up the antagonism between Aaron and Negan, but with Mary murdered, it'll be Beta who Aaron will really want to get revenge on.
Though Alpha is dead, AMC's Whisperer War isn't over yet. The remaining episodes in The Walking Dead season 10 will likely see insanely dangerous hand of his to take him out.