Strangling the dog was a strong moment? The hell it was.
It was so obviously going to happen from the beginning of that scene on. And it wasn't even well executed. Yeah, he hugged it, it turned, then he choked it while looking bored. Great acting my ass. The whole idea of him hugging it when it's most likely going to turn any second was stupid enough -- sole friend or not, he knew it was going to happen.
'sides, if he used the serum that un-turned one of the rats and nearly killed the human, how did the dog NOT die from it? If he thinks he has to save mankind even though mankind has turned, why does he not care about keeping and eventually saving his best living friend?
BAD script, BAD acting.