Walt did let Jesse's girlfriend Jane, choke on her own vomit and die right in front of him, when he could have saved her. He also had Gale killed. Spoiler What if Walt did poison the kid? When Jesse tells Gus that he was poisoned, Gus seems genuinely surprised. I think Gus realized that Walt did it to turn Jesse against him while walking to his car, and that's why he stopped. I read somewhere (that I can't remember), that Walt is going to commit an unforgivable act this season. But considering how unpredictable this series has been, I wouldn't be surprised if Walt Jr. poisoned the kid's pancakes while standing in a hallway. Hank-"Someone doesn't like the way i've been spending my free time" Walt Jr.-"What, minerals" Hank-"Yes Walt Jr, the Cartel is coming to murder me because of my mineral habit"