The last of two ending
This is the actual last 10 minutes of the game.
Ellie: Im going to kill you!
Abby: Just do it
Ellie: Actually I´ll set you free let´s get out of here
Abby: Ok
Ellie: You know what, I want to fight you or I will kill this kid
Abby: Ok
Ellie: about to drown Abby I forgive you, just go
Abby: Ok
This game's writing is just genious ?D
@ChristiJunior
Nah... it's just a game balanced for their needs.
Why not just provide a Story/Cutscene-Only option with zero gameplay at this point?
@ChristiJunior
How about the integrity of both main charakters killing hundreds of innocent people just so they can reach the target and then... let the target go.
Wow... such a redemption. If you see a murderer kill 114 people, but then you see them spare one, it's all ok... 
I actually didn't have a problem with how they did it because of the very real character development, the great gameplay, gripping narrative and memorable locales.
It did this very same trope but it was far more impacting because of just how everything lined up.
@Shining @ChristiJunior
To be honest, I hate that trope in general.... with ONE exception. It must be both painful and pragmatic to safe that one life.
Luke saving Vader for example. When Luke didn't kill Vader, he did it from pure moral standpoint, but that decision had a further impact on the story, since the vader then did decide to kill the emperor.
but in most cases, they just save that life, and that's all? It has no meaning, if the meaning of that act ends there.
Here's what doesn't make sense: Not killing the creature who murdered your father figure because of a brief flashback of the victim you want to avenge. Not a flashback of him condemning revenge, not a flashback of him being hurt by his own lust for revenge, but a super-short flashback of him with his guitar. Maybe it's 2Deep4Me, maybe the guitar represents the preciousness and fragility of life to Ellie, but to me it just looks fucking retarded.
For all we know, the flashback is of the tree the guitar was made from wishing that everyone involved just used it to fucking hang themselves, and by proxy, the player
How's that for symbolism
It could have been avoided, yes - but the inevitable happened anyway, because of their particular allegiances
TLoU2 has no vision beyond showing you something shocking for its own sake.