Who did Pope kill in Outer Banks?
For four seasons, Pope Heyward was the Pogue you'd want holding the map. Careful, book-smart, the one who read the historical documents while everyone else was jumping off things.
Then the Season 4 finale handed him a gun, and Outer Banks became a slightly different show.

The short answer
Pope killed Lightner, a member of the Lupine Corsairs, the artifact-hunting mercenaries who spent Season 4 making everyone's lives miserable. Lightner is the one who murdered Captain Terrance earlier in the season. Terrance was Cleo's surrogate father and the guy who kept John B and Sarah alive when they were stranded back in Season 3.
So when Cleo ends up wounded and face to face with the man who killed the closest thing she had to a dad, she can't pull the trigger herself. Pope hesitates once. Then he does it.
The gut-punch isn't that Pope shoots someone. It's that Cleo, who once talked him out of killing Rafe, is the one telling him to fire.
Why it lands harder than the other deaths on this show
Outer Banks kills people the way other shows change outfits. Ward. Big John. JJ, stabbed by his own biological father in that same finale, which is the death everyone remembers from that episode.
But Pope pulling the trigger is different because Pope is the character the show built specifically to not do that. In Season 3, Cleo stopped him from shooting Rafe. In Season 4, she's bleeding and asking him to finish it. The reversal is the point.
He does not get over it
Season 5, the final season that dropped August 20, opens with Pope in pieces. Jonathan Daviss, who plays him, was blunt about it with The Hollywood Reporter:
"If you watched the last season, he's in a bad place. He protected Cleo and he did what he had to do, took out that Corsair. And he's just kind of dealing with the mental stress of that on top of losing one of his best friends."
Netflix's own materials describe him as dealing with PTSD from the shooting. Daviss, talking to Brit + Co, went further: "He's not the person that started the show with the same wants." Which, for a character who started the show wanting a scholarship, is a long way to travel.
The rest of the Lightner fallout, briefly
- The Corsairs don't just evaporate. Their shadow hangs over the Pogues into the final season alongside Chandler Groff, the man who actually killed JJ
- Pope also gets arrested in that finale stretch for attacking a cop to stop him from shooting JJ, and nearly ends up in the Marines. It's a busy few episodes for a guy who used to be the responsible one
- By the series finale, he's the one walking Sarah down the aisle, which tells you where the show wanted him to land emotionally
Where he ends up
Without wrecking the finale: the show's creators told Deadline that Pope proposes to Cleo twice in the final season, and Pope and Cleo end up in Tannyhill, the ancestral home of Denmark Tanny that Pope spent the entire series trying to reclaim on paper.
So the answer to "who did Pope kill" is Lightner, a Corsair, in defense of the woman he marries. The answer to "what did it cost him" is basically the whole last season. Outer Banks was never subtle, but on this one, it was at least consistent.