I was waiting for them to come full circle with Ellie's path but instead was like only 40% of a story arc.
They tried to show how the killing was wearing on her mentally a few times (Mel specifically) but it didn't really have any culminative effect. If they had gone for a slow decent into madness like Spec Ops: The Line I would have been on board. She had the one panic attack (for what happened to Joel, not her own actions btw) that pushed Ellie into the ending sequence but they didn't go far enough with to really "earn" it. Her characters purpose in the greater plot felt incomplete.
At the very end, I honestly thought the story would have veered toward forgiveness (for both Ellie and Abby) and anti-violence. They had a cool opportunity to do something with the gameplay where the characters came to the same understanding as the player that ALL OF THIS VIOLENCE IS UNNECESSARY. The WLF/Seraphites war was literally just circular violence breeds violence. Especially for Abby, who had been on both sides of this thing, having killed plenty of Scars, only to realize they are human beings just like her. "No more killing Lev. This has to end" would have been cool with an extended stealth, non-murder sequence. Instead the designers placed fuel canister ammo in the Seraphite village so Abby can commit war crimes with her flamethrower.