I think that if they let Ellie decide , and allowed her to tell Joel that she wants that, he wouldn't have reacted that way. They didn't give him a chance to say goodbye, see her, and threatened him.

“Cordyceps grows inside the brain”. Man, what a powerful line for me. I love The Last of Us Saga.

I played the game with my dad watching, like a film for him.

I asked him, what would you do if it was me?
"Exactly what he did."

Then I understood Joel made the right decision.

He did what a father was supposed to do. Protect her and he did.

This ending perfectly aligned with how the series progressed. The point of sacrificing Ellie was to cure Cordyceps, but if you really think about it, Cordyceps was never really the main antagonist at any point of the series. The main antagonist was humans and how they corruptly they handled the pandemic. Joel alluded to that when he said earlier that he didn’t believe in trying to save the world. Even on the off chance that Cordyceps was cured, you can’t cure the dark side of humanity.

There was never any conflict to me. Joel lost his own daughter. There was no way he would go along with that plan. As a parent, I could never bring myself to. It goes against everything that makes you a parent.

Honestly if they had just asked Ellie she probably would have agreed to the procedure.

If you want a better aspect of why Joel made this decision

Ellie at the age of 14 doesn't need to make a decision at all that would led her to her death, and if she had said no they would likely still have had forced ellie or persuaded her maliciously to undergo the procedure anyways.

The slight music drop as Joel says “I do” is a damn masterpiece! You can feel that in your bones

I had heart surgery and even my mom sided with Joel. Then she said "why kill the only immune person right away?"

"i'm the only one to understand" is such a petty move by Marlene, she shouldn't said that.

The show makes Joel's decision less ambiguous. In the two flashbacks, we see premiere fungal scientists say there is no cure for cordyceps and that a jump to humans would be catastrophic. The limited resources and scientific knowledge of the post apocalypse give little hope for a cure even with Ellie. Experimenting on her would have been a needless waste of her life

The last of of us is fascinating, many people want black and white decisions , but often it isn't that simple.

1:45 "He *thinks*"

Joel: "You don't understand..."
Marlene: "I do..."


Marlene: "I don't have a choice."
Joel: "I do."

Proceeds to kill all Fireflies.

A father who was willing to sacrifice all of humanity to save his child. If that’s not love I don’t know what is.

I bet the reason they did not ask Ellie is because they think she might refuse.

The thing is with how the world is joel doesn't make the right choice, or the wrong choice, joel just does what he thinks is best for him and ellie.  To me, the whole point of the show is that cordyceps wasn't the problem, cordyceps is just something that happened. People are the real problem. Cordyceps doesn't think about who it kills. It spreads because that's its nature. People, however, have the ability to think and do what is necessary for their survival. People are willing to drop their moral ambiguity and do horrible things in order to survive. The show and the game just show that when push comes to shove and humanity and morality are taken away, there are two types of people. Those wanting to hold on to it and those willing to let go of it.

"he THINKS it could mean a cure" so you're not sure huh? That would be the 1st red flag

I've watched this scene many many times in the game and in the series. It still hurts everytime.