Re: Fatal Flaw?
I haven't seen The Lives of Others yet, but I'm not really sold on the other examples you mentioned.
In Zombieland, I would say that Columnbus is definitely the protagonist, rather than the girls (they even serve as antagonists, albeit briefly). When the girls go their own way and wind up in trouble, he's the one who decides to go look for them and guilt trips Tallahassee into helping him. He is the proactive character.
I dont buy that the girls are the protagonists by virtue of tryng to reach the safety of the West Coast. Only the younger of the two girls actually believes that there is safety left in their world. All the characters share the same goal, which is simple survival, and trying to make sense of the new world they find themselves in.
With The Terminator, I see Reese's role as being similar to Obi-Wan's in Star Wars. He's there to protect the protagonist (Sarah Connor) and fill her in on the bigger world that has just opened up to her. If you take the Joseph Campbell slant, Reese is The Wise Old Man, teaching Sarah how to make the explosives is his handing out the Magical Weapons, just like Obi-Wan with the lightsaber.
And just as with Star Wars, it is the protagonist (Sarah Connor) who vanquishes the Antagonist (The Terminator) with the wisdom and weapons given to them by the mentor figure.
On a completely unrelated note, I have discovered that I cannot type the words Sarah Connor, without hearing Arnold Schwarzenegger saying it in my head.
"Only nothing is impossible."
— Grant Morrison