Seeing how close Ezio is to death in Embers. Although he's certainly able to keep up with Shao Jun and take out a few Chinese mooks (Including a Juggernaut mook), it's clear that death is coming for him. And at the end of Embers, it does.
What makes it particularly heartrending is if you have played the three games featuring Ezio, you have literally been with him since the day he was born. You're with him when he comes into the world, and you're with him when he leaves it.
…I can't have been the only one who thought of those three words as he died.