The much-anticipated final episode of "Breaking Bad" drew the cult TV show's largest ever audience -- 10.3 million viewers -- but there were also more than 500,000 illegal downloads, figures show.

The series, centered around once humble chemistry teacher turned drug lord Walter White, ended Sunday with a thrilling climax to its fifth and final season a week after winning best drama at the Emmys, television's Oscars.

In doing so it drew 3.7 million more viewers than the penultimate episode seven days earlier, which itself had set a series record at 6.6 million, the ratings tracker Nielsen said, cited by industry journal Variety.

"Breaking Bad," set in the dangerous world of methamphetamine (crystal meth) trading, which White rises to dominate, mesmerized viewers with a cocktail of meticulously crafted plot, fine acting and scenic camera work.

But it was the stunning metamorphosis of White's average guy persona into that of a veritable monster that ultimately captivated audiences.

White, played by actor Bryan Cranston, became a meth manufacturer in the New Mexico city of Albuquerque, having learned at age 50 that he had terminal lung cancer.

With his bank account all but empty the lead character outwardly took the drastic decision to pay for his treatment and provide for his family, but the underworld he enters eventually captures him in unanticipated fashion, catapulting him into the role of a criminal kingpin feared by his rivals.

But much as he manages to achieve his original goal -- at one point raising around $80 million for himself -- his life spirals out of control and ends in tragedy for many of the characters involved in the show.

The final episode's record ratings, however, were less than the biggest audience for the "The Walking Dead" on 12.4 million, but almost three times the largest-ever figure for award-winning advertising drama "Mad Men," which drew 3.5 million for the first show in its fifth series.

While AMC, the cable channel which broadcasts "Breaking Bad," will be happy with the high ratings, they will be less pleased at the number of people who watched the final episode through illicit means around the world.

The show was illegally downloaded more than half a million times within 12 hours of the first illegal copy appearing online, according to online piracy news website TorrentFreak.

Australia had the largest number of illegal downloads with 18 percent of the total, followed by the United States on 14.5 percent, Britain on 9.3 percent, India on 5.7 percent and Canada 5.1 percent, it reported.

Other countries in the top 10 for illegal downloads included the Netherlands, Poland, the Philippines, France and South Africa. TorrentFreak said the show was illicitly watched even in places where it was available legally.

"Looking at the list of countries... it's clear that piracy is still rampant, even in countries where people do have the option to watch the show legally," it said.

Twitter comments surged before, during and after Sunday's "Breaking Bad" episode, making it the top ranked Social media buzz generating show of the evening, according to the SocialGuide tracker of social media traffic.

The epic drama triggered three times as many tweets as the next most talked about event, an NFL match between the New England Patriots and Atlanta Falcons.

"I can't even believe that the ratings have increased with each episode — I just think it’s wonderful," "Breaking Bad" creator Vince Gilligan told Entertainment Weekly.

"People have asked me, 'Does it make you want to go on and do a bunch more episodes now?' Just the opposite. It makes me think, through quite a bit of good luck being involved, we really did pick the right moment to exit the stage, and I feel even more confident of that now than I did before.”