The finale of Better Call Saul season 5 suggests Lalo Salamanca (Tony Dalton) will hunt down Nacho Varga (Michael Mando), but there's a good chance it'll actually be Gus Fring (Giancarlo Esposito) who kills him in season 6. Within Better Call Saul season 5, episode 10, "Something Unforgivable," Nacho drives Lalo to his home, a heavily guarded hacienda located in a remote section of Chihuahua, Mexico.
Deducing that he is stuck in Chihuahua, Mike Ehrmantraut (Jonathan Banks) suggests sending someone to remove Nacho, especially since Lalo’s assassination has been arranged for that evening and Nacho will get caught in the crossfire. Spying value in Nacho’s unfortunate situation, Gus decides instead to use him as an inside man. Nacho then receives a call that informs him to open the back gate of Lalo’s residence at 3 a.m. After distracting Lalo by setting a fire in his home, Nacho opens the back gate, lets the four assassins into the compound, and escapes the premises. After killing the four assassins on his own, Lalo concludes that Nacho was involved in the attempt on his life and sets out for revenge, but Lalo isn’t the only person who would benefit from Nacho’s death.
Now that Lalo believes Nacho was involved in his attempted assassination, Nacho no longer serves a purpose to Gus as his mole within the Salamanca drug empire. Nacho has been working as an informant for Gus ever since he discovered that Nacho caused Hector Salamanca’s stroke and began blackmailing him in Better Call Saul season 4. During the season 5 episode “Bad Choice Road,” Gus informed Mike that he wasn’t willing to release Nacho from their arrangement because he still proved useful to their operation. However, now that Nacho’s cover is blown, the most pragmatic move for Gus to make in season 6 would be to kill Nacho because he’s now a risk to his overall plan for revenge against the Juárez Cartel. With no loyalty tying him to Gus, if Lalo were to reach Nacho first, it’s possible that Nacho will tell Lalo that Gus was behind his attempted assassination, putting Gus's entire operation at risk.
Not only would Gus benefit from killing Nacho himself, but past events involving Werner Ziegler (Rainer Bock) have proven that Gus is 100% capable of killing someone who poses a threat to his plans. Gus is once more faced with a similar dilemma to the one that occurred during the season 4 finale of Better Call Saul, when Lalo was closing in on Ziegler’s trail and almost discovered that Gus was constructing his own super-lab independent of the Juárez Cartel. After Ziegler unknowingly blabbed some of the details about the construction process to Lalo over the phone, Gus ordered Mike to kill Ziegler since his loyalty and discretion were in question. When weighing the risk that Nacho poses in comparison to Ziegler, Gus would have zero qualms deciding to kill Nacho, since he has more valuable and damning information that could completely dismantle Gus's plans for vengeance.
While Gus would certainly benefit from killing Nacho before Lalo finds him, such a plan would cause some tension between Gus and his right-hand-man Mike. After Mike was ordered to kill Ziegler during the finale of season 4, Mike spent a great portion of Better Call Saul season 5 mulling over his guilt for killing the innocent German engineer. While Mike has avoided killing for Fring in the past, Ziegler was the first person Mike killed for the sake of Fring’s drug empire, which may be why he grieved over his death so thoroughly. While Mike seems to be slowly coming to terms with his role within Fring’s organization, it doesn’t seem like Mike will be all too willing to kill Nacho for Gus, especially since he adamantly suggested that they should cut Nacho loose after he held up his end of the deal within the episode "Bad Choice Road."
If Gus asks Mike to kill Nacho for him within the sixth and final season of Better Call Saul, it'll be a great test of Mike's morals and may be the final push that makes Mike become the ruthless version of himself previously seen on Breaking Bad.