SPOILER WARNING: This shouldn't be needed, but just in case, spoilers for all 8 seasons of Dexter follow. Dexter is one of my all-time favourite TV shows. It had a great concept (taken from a great book) that hadn't really been done on television before. Season 1 introduced us to Dexter Morgan, a serial killer who just so happens to work for Miami Metro Homicide as a forensics expert. Let's not forget that he only kills bad guys too. It's a mouth-watering premise and the first season didn't disappoint. The trend continued with Season 2 and introduced genuine peril by having Dexter's crimes being discovered, yet his crimes as the infamous 'Bay Harbour Butcher' became attributed to a shady detective who had been harassing Dexter. We've seen Dexter escape from countless inescapable situations and come out unscathed, but it never felt forced or contrived until after Season 4. Season 4 was the absolute highlight of Dexter for me, which revolved around a new serial killer named 'Trinity', played by John Lithgow. Season 4 had a similar sense of jeopardy to Season 2, but Lithgow's performance - and indeed, Michael C. Hall's - mesmerised. Keith Carradine's excellent turn as Frank Lundy also helped bring a sense of purpose to an already brilliant season. The season ended with one of the biggest twists in the entire history of the series after it was revealed Dexter's wife Rita had been murdered by Trinity before Dexter could kill him. The unveiling of the death hit like a sledgehammer. It was brutal and would be a massive game changer for the show. The brave move to kill off Rita showed that none of the main characters where safe. If Rita could die, why couldn't Deb? Or any of the other supporting cast? Unfortunately this proved to be Dexter's last big hurrah. Dexter has been on a downhill slope ever since. After bringing on several new writers and a new showrunner, something went badly wrong. Dexter went from being one of the most original shows on television to becoming derivative, repetitive and above all else, predictable. Here I'm going to try and pin point the worst moments in the series and what has led to the downfall of one of the best shows around. Click on to see what comes first...