Who: Drug dealer
How: Under the guise of teaching the dealer his meth recipe, Walt created deadly phosphene gas and trapped Emilio in the RV to asphyxiate.
Why: Tried to rip off Walt and Jesse on their very first deal, was almost certainly going to kill them.
Who: Drug dealer
How: Choked with a bike lock.
Why: Krazy 8 survived the phosphene gas, leading Walt and Jesse to keep him locked up in the basement. While Walt formed a connection with Krazy, he realised that the gangster was planning on stabbing him with a piece of broken plate.
Who: Jesse's heroin addict girlfriend
How: Watched her choke on her vomit after an overdose, did nothing to help.
Why: Umm? Walt was worried that Jane was a bad influence, dragging Jesse off the rails. It's debatable whether Walt did it to save Jesse, or just to keep him as an ally in his war against Gus.
167 passengers and one air traffic controller
Who: Every passenger on two aeroplanes that collided over ABQ, the air traffic controller responsible, plus one pink teddy bear.
How: Bear with me. Walt let Jane Margolis died. Her father Donald, an air traffic controller, was so wracked with grief he couldn't concentrate on his job and made a fatal error. He later killed himself out of guilt.
Why: The effects of Walt's action ripple out and corrupt everything.
Justification: Chaos theory.
Who: Dealers who killed Jesse's friend Combo and his girlfriend's little brother. Jesse was just about to shoot them when...
How: Walt ran them over with his crappy Pontiac Aztec, then shot them in the head.
Why: To protect Jesse from himself.
Justification: See above.
Who: Nerdy lab assistant Gus brought in to replace Jesse.
How: Instructed Jesse to shoot him in the face.
Why: To make sure only Jesse and Walt knew how to make the crystal blue meth, so Gus couldn't replace them.
Justification: A tough job market.
Gus Fring and Tio Salamanca
Who: Gus the drugs kingpin/fast food restaurateur and his old enemy Tio from the Mexican cartel.
How: Walt rigged Tio's wheelchair to explode when Tio rang the bell he used to communicate. (How often do you see the exact same story on the news?)
Why: It was kill or be killed with Gus.
Who: Tyrus the dead-eyed henchman, and two nameless guards at the superlab.
How: Tyrus died in the wheelchair explosion, while Walt straight up shot the other two.
Why: To rescue Jesse from the lab and burn it to the ground, destroying all evidence.
Justification: Collateral damage.
Who: Sardonic bodyguard and assassin, begruding business partner after Gus died.
How: Shot him with his own gun.
Why: Ostensibly because Mike wouldn't tell Walt the identity of nine witnesses that could tie Walt to Gus's operation. Really, it was because Mike insulted him and Walt lost his temper.
Justification: Saw red.
Nine witnesses and one lawyer
Who: Former employees of Gus.
How: Shivs and fire. All of the men were being held in different prisons, but Walt hired a group of Neo-Nazis to kill them all simultaneously. It was very Godfather.
Why: They knew too much.
Justification: Tying up loose ends.
Hank Schrader and Steve Gomez
Who: Walt's brother-in-law and his partner in the DEA.
How: After a massive falling out over poisoning a child (always a sticky issue), Walt called in his old friends the Neo-Nazis to kill Jesse. Jesse tricked Walt into revealing the location of his money, leading the chemist to panic and call in the white-supremacist cavalry. On seeing Jesse had teamed up with Hank, Walt immediately changed his mind and told the Nazis not to come. It was too late. They showed up anyway and a massive gunfight ensued. Despite Walt's begging, they then executed Hank and took the money for themselves.
Why: We've moved past questions like 'why'.
Justification: Walt has been deposed. He's no longer king.
Who: Jesse's girlfriend and mother to young Brock.
How: Enraged by the death of Hank, Walt spotted Jesse hiding under a car and demanded the Nazis finish the job. Instead, they asked if they could take him back to their lair and torture him for information. Walt agreed. Unbeknownst to him, the Nazis chained Jesse to their own meth lab and demanded he start cooking or they would hurt Andrea and her child. When Jesse tried to escape, they shot Andrea on her own doorstep, while Brock played inside. Jesse was forced to watch. All because Walt couldn't accept responsibility for Hank's death.
Meth users and the wider populace
Who: The hopeless addicts who use Walt's products, and everyone else his selfish quest has destroyed.
How: Andrea and the crashed planes show how Walt has spread like a cancer through Albuquerque and beyond. How many people have died using, selling and fighting over his product, or through unforeseen consequences of his actions? We can't know. In many ways, Walt is directly responsible for almost every death in the series. As in chemistry, he was the catalyst. The reaction is now out of control.
Why: Walter White.
Justification: Walter White.
Thanks to Breaking Bad Wiki. Disagree with our choices? Who have we missed? Who will survive the last episode? Tell us below!
Breaking Bad concludes on Netflix on Monday