Hanzo doesn't talk much, and explains it's because he 'talked too much'. He shows off his cut fingers to explain — specifically, more than one, which partially shows how valuable he must be to the Yakuza, to be allowed to live twice. But smarter than that, by pretending that he doesn't understand English, he gets to listen in on everything the other characters are saying, whether it's about him or about their plans, and they don't worry about him hearing it. He only speaks when he's sure he can trust them.
When the Predators' hell-hounds almost kill Isabelle, Edwin cries out in horror and anguish that she's going to be killed. Given how later in the film, Edwin turns against the heroes and tries to murder Isabelle, Edwin being upset about Isabelle isn't because he was falling in love with her or growing attached to her... but because he planned on killing Isabelle himself and didn't want her stolen from him.
Moreover, Edwin is strongly implied to be not just a killer, but a serial killer. Despite what many movies say, that's a pretty specific label, which includes usually a favored victim type, one variety of person which that serial killer gains the most (or only) gratification from killing. Isabelle may be the only one on the planet who fits Edwin's victim type, and thus would be the only one it would be satisfying for him to kill.
Edges over into Fridge Horror when you notice that he didn't actually yell out a Big "NO!" until Isabelle placed her sidearm against her own head, evidently preferring to shoot herself than be ripped apart by the hound. Was he merely outraged that he was losing a potential kill, or was he doubly outraged because he'd previously lost one to a similar Better to Die than Be Killed choice by a defiant victim? Could be that was why he took up studying paralytic poisons, to ensure no future target would be able to snatch the scalpel from his hand.
