9. Someone Will Snitch
While the chances of Walt and Jesse snitching on each other are slim to none, one could imagine other characters turning state evidence to protect themselves, specifically Skyler if she is ensnared in any of Walt's plan, perhaps as an accessory through her money laundering operation. The other likely candidate would be Saul Goodman; though the veiled legitimacy of his business and the attorney-client privilege keeps him protected to an extent. An outside possibility might be Mike Ehrmantraut, perhaps to protect his family if they are threatened, but one expects he is more likely to flee if he is compromised. Whoever snitches, this could very well be how Walt ends up being caught or at least exposed to Hank.