"Never buy it all at one place"...

... i think that is the last moment you see walt before he turns to a complete villain.

He is out getting stuff to fill his days with puttering and fixing things for his family.

When he sees the junior meth maker, he decides to flex his knowledge and help a brother out.

As he does so, he realizes the home improvements were meaningless to him- what he really wanted to do was make meth.

I am sure it has been posted here a thousand times before, so forgive me.

... but i really love the symbolism of him abandoning his home project and stalking out the door to scare the shit out of his possible competition.

Walt did many villainous things up to that point, but right there is where he consciously made the choice to embrace that over all else.