As the age-old adage goes, the show needs to go on. But what marks a great show? The ability to keep the last episode as engaging as the first. A lot of shows start on a promising note, and then lose their way for a variety of reasons. Which is why shows like a Breaking Bad or a Game of Thrones, become pop-culture legends when they manage to end on a satisfactory note. 

Here are 15 shows which started off quite well, but soon found themselves marinading in the vessel of mediocrity:

1. Lost

The show which became the stuff of TV legend with its pilot, began to falter during its run of six seasons. Many fans criticised the fact how the runners built up the finale with too many secrets and the pay-off wasn't as convincing. The show by JJ Abrams and Alex Kurtzman still has a cult following of its own, but even the biggest fans concede the finale didn't live up to the promise.

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2. Heroes

Even though a lot of the fans know the decline of the first season was to be blamed on the writers' strike, but the sheer promise of the first season meant that the fans felt excessively let-down by the following three seasons. The characters seemed to be brooding for no reason at all. Season three and four was subject to really harsh criticism by fans and critics alike, after which the show was pulled off air.

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3. Dexter

A show with one of the most frightening, intriguing protagonists since Hannibal Lecter, Dexter quickly became its own doom. The show which was highly rated till about the fifth season, went completely haywire in its last three seasons. Even though Michael C Hall's titular performance was applauded till the very end, the fans found the finale a tad anti-climactic. The numbers didn't fall though as Dexter's finale showed the most number of viewers for Showtime ever.

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4. The Big Bang Theory

Opening to mixed reviews, the show helped its actors shoot to super-stardom including Jim Parsons as Sheldon, Kaley Cuoco as Penny and Johnny Galecki as Leonard. The actors salaries became front-page news on gossip websites, however the show fell out of favour with the critics after Season 4. The show is on its 9th season now, and is still running because of a loyal base among the audience, however, recent seasons of the show have been panned.

Source: Playbuzz

5. Suits

Turning Gabriel Macht's Harvey Specter into a mantra-spouting lawyer and Patrick J Adams into another cute kid with the brains of a genius, Suits set the ball rolling in the first two seasons. And then the show stopped being itself, and focused on the romantic relationships of both its leading men and their petty fights with partner Louis Litt. Since then the show has gone downhill, and the sixth season has the lowest viewers at 1.6 million as compared to 4.64 million during the first season.

Source: USAToday

6. Newsroom

Aaron Sorkin's show about the workings of a primetime news show had all the ingredients for a Sorkin show. Idealistic characters, machine-gun dialogue, the office romance, Newsroom found its fans and also had its fair share of detractors. The show knew what it was and celebrated its feel-good, Frank Capra-element through the first two seasons. And then came the third and the final season - full of potential, where the show would tackle the emergence of new media vs old. The show let its audience down with a sentimental finale which just felt full of saccharine.

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7. Fringe

JJ Abrams and Alex Kurtzman's show about the fringe science allows humans to delve into border-line sorcery with powers of telekinesis and alternate reality. And even though the show followed the old formula of cop accompanied by brainy scientist, it was interesting for the first two seasons. The numbers plummeted from 9.13 million viewers to 3.12 million and just showed how people lost interest in the show's final three seasons.

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8. Weeds

The show follows the story of a mother with two teenage sons based out of California, who sells marijuana for a living. The dark humour of the series got high critical acclaim for the first three seasons. The series would run for five more seasons without its usual fan following and the critical appreciation, which took a dive after the family moves to San Diego, Seattle and then Dearborn.

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9. Coupling

This show hailed by many as Britain's answer to Friends, ace-screenwriter Steven Moffat basked in the glory of his two well-received seasons. The show's third season was when it all began to fall apart for many fans and Jeff's departure in the fourth season meant the show continued its descent. The show wasn't completely unwatchable by the end, but the difference was noticeable.

Source: Bustle

10. Prison Break

One of the most addictive TV series of its time for its vast array of characters from the crazy T-Bag, to the protagonist Michael Scofield and his photographic memory, Prison Break was quite the thrill ride for the first two seasons. And then the show began going around in circles. Even though fans stuck by it till the end of Season 4 even the purists swore the show wasn't as brilliant as it began. The show is being renewed with a new season, hoping it will have a better second innings.

Source: Idigitaltimes

11. Pretty Little Liars

The show started out knowing who it was catering to, and was quite fun in the beginning. And then the show progressively went from wow to WTF! Starting off as a teen show, it quickly changes tracks to an unconvincing murder-mystery thriller. Even though the show kept its audience numbers, a lot of fans from the initial seasons became more and more aware of how bad the show had become.

Source: Etonline

12. Supernatural

Still running after a mammoth 12 seasons, Supernatural supposedly lost its plot somewhere after the much-loved finale of Season 5. The Winchester brothers continue to chase spirits in their Chevrolet Impala, sadly in the recent seasons it has been making less and less sense.

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13. Castle

The show was another run of the mill police teaming up with a professional (in this case a crime novelist) who helps with solving crimes in the nick of time. However, even though the show was a fun watch for the first few seasons, it quickly got repetitive. As Castle dragged on to its eighth season, lead actors Stana Katic and Tamala Jones announced they wouldn't return for a ninth season. The show was then cancelled.

Source: fansided

14. Arrow

DC's Arrow even though drew its parallels with the comic universe's favourite son, Batman, the sleek action caught quite a few eye balls. The fans were interested how the show would spin the famous characters like the Ra's Al Ghul in Arrow's narrative. The second and the third season got criticism for focusing too much on the romantic tracks. The fourth season got panned outright, however it was renewed for a fifth season which is ongoing and the viewership continues to fall in the midst of unfavourable reviews.

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15. How I Met Your Mother

The equivalent of Friends for millennials, How I Met Your Mother began as a genuinely funny sitcom with popular characters including Ted Mosby, Robin Schrebatsky and Barney Stinson. The series stretched on to 9 seasons and even its most ardent fans swore that the show lost its charm towards the end and became predictable. A massively disappointing finale meant that How I Met Your Mother wouldn't get the title of being the Friends of this generation.

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Well, what can you say other than, it could have been better.