SPOILER ALERT: This article contains a look back at the first four season of Breaking Bad. Spoilers abound.

Walter White’s moral compass is kaput. Over the course of four seasons of Breaking Bad, we’ve witnessed Walt transform from a muddling meth cook to a murderous, manipulative drug maven. It’s been a stunning descent, punctuated by some truly shocking incidents along the way.

Here are four pivotal moments in the moral devolution of Walter White:

S1, E3 – The Cat’s in the Bag…
It’s safe to say that Walter’s entry into the meth game got off to a rocky start. Not only did he nearly get himself arrested with his first batch, he and Jesse immediately ran afoul of local dealer Krazy 8.

However, through a combination of luck and chemical know-how, Walt and Jesse managed to gain the upper hand on Krazy 8, who ended up chained to a pole in the basement of Jesse’s house.

During an afternoon spent guarding the prisoner, Walt took some time to open up about his cancer diagnosis –the reason he got into the drug game in the first place – before brutally strangling Krazy 8 just when he seemed to be on the verge of setting him free.

S2, E13 – ABQ
With Jesse falling under the control of a persuasive fellow meth-head, Jane, and the pair planning to blackmail Walt for their share of his latest drug deal, Walt knew he had to act.

Fortunately for him, the only action he needed to take was to stand by and watch as Jane choked to death on her own vomit during a drug-induced stupor. It wasn’t Walt’s first murder, but his “murder by inaction” remains one of the most shocking illustrations his willingness to sacrifice others to save himself.

S3, E13 – Full Measure
It would be hard to top the double murder he committed in the previous episode of season three – running over a drug-dealer with his car and shooting another one point blank in the head – but Walt ordering a hit on his former lab partner Gale proved once again that anyone is expendable if it means Walt will be allowed to continue to “provide for his family”.

S4, E13 – Face Off
This episode contained a double blow. After spending the entire season on the back foot, Walt managed to turn the tables on Gus and off his nemesis with a spectacular explosion.

But the real shock came when it was revealed that Walt set his entire plan in motion by poisoning an innocent child, in order to drive a wedge between Jesse and Gus and reveal a chink in his foe’s armour.
 
After all this, the question we’re left with is: what’s next for Walter White? Find out in the season five premiere of Breaking Bad, Thu, 27 Sep at 21:30.