Altair and 16 were already dead. I didn't really feel sad seeing Altair die, but happy, because his death was a peaceful one after saying his goodbye with Darim and the Polos. I wasn't too attached to 16, plus, he remains a total mystery throughout Revelations, which ****ed me off a lot. Yusuf's death was the most moving for me, but it also ticked me off, as I wanted to see much more of him. He is the second supporting Assassin ally to die in an AC game, before Mario. What makes Yusuf's death sad is that he died trying to keep the promise he made to Ezio in order to protect Sofia.