Phil isn't just strangling him - he can feel Phil's nails digging into skin. He can't tell if he can really feel it bleeding or if he's just imagining it in his last moments.

The Once-ler's mouth is open wide but he can't breath in no matter how he tries. For a moment the struggle intensifies in a final bit of desperation, but...it can't last.

He lets go of Phil's hands. All of the fight in the Once-ler vanishes, and his entire body goes limp and heavy in Phil's grip.

The light fades from his eyes and he is gone.