From 1989 to 1994, Leo Rossi stars in this 4-part series of non-stop thrills. Here’s how we ranked the Relentless movies, from least to greatest.

When it comes to psychological thriller movies, there are only a few that successfully places the viewer into the shoes of the characters. The best thriller productions provoke the kind of emotion that has viewers yelling at their TV screen, begging their favorite character to turn around or not to go into that dark, creepy room. Now take that emotion and spread it across 4 films in 5 years: that's the Relentless tetralogy.

The series varies from film to film based on who directs it, for better or worse. One constant – Leo Rossi’s performance as Sam Dietz. We watch Detective Sam Dietz grow as a member of LAPD, making a career chasing serial killers who terrorize Los Angeles. Throughout his journey, the detective is paired with several partners and hunts serial killers with differing methods of killing the innocent. To make things more complicated for the New York transfer, his love interests are continuously placed in the middle of the investigations, making it a heart-wrenching experience for the viewer. Not many people know what it’s like to hunt serial killers, but potentially losing the person you care about is something that will make anyone’s stomach drop.

Relentless 2: Dead On

Relentless 2 cover
CinTel Films

In this film, Leo Rossi’s character takes on another serial killer who was a former Russian soldier. As Sam becomes more involved with his job, his family life suffers significantly. To make things more complicated, Detective Sam Dietz must overcome a new partner from the FBI who repeatedly sabotages the investigation, by not being fully transparent about their ties to the Russian killer. Sam takes matters into his own hands and tracks down the killer in his typical relentless fashion. The subtitle may read “Dead On”, but Relentless 2 very well missed the bar set by the 1989 original. The departure of director William Lustig, combined with a direct-to-video release resulted in a sequel that left fans seeking more. The movie received a mediocre rating, but the flop felt more disappointing since it followed the original after several years of built-up anticipation.

Relentless 3

Relentless 3 cover
CinTel Films

Detective Sam returns to Los Angeles to consult on a case that was supposed to be a pleasant change of pace for him, leaving the high-stress life of catching serial killers. However, things don’t go quite as planned after a failed marriage. A serial killer (William Forsyth) who was once arrested by Sam himself, decides to enact his revenge by targeting a woman near to Sam’s heart, throwing Sam right at the forefront of another serial killer case. So much for a relaxing homecoming! Overall, this movie felt very underwhelming. William Forsyth has an impressive resume but didn’t captivate viewers in Relentless III quite like he did in other horror classics like this Rob Zombie movie. This falls more on the small-budget production rather than his solo performance.

Related: 10 Best Psychological Thrillers, Ranked

Relentless IV: Ashes to Ashes

Relentless IV cover
CinTel Films

Relentless IV is the final chapter of the heart-pumping series featuring Leo Rossi. Unlike the random murders that take place in the 1989 original, Relentless IV, directed by Oley Sassone, displays a serial killer who ritualizes heinous acts towards women. In this sequel, Detective Sam Dietz is paired up with a female partner (Colleen Coffey). To crack this case, the detective will have to balance a thin line between work and play. The subject of his attention, a psychiatrist played by Famke Janssen, holds key pieces of information that can break the case but is conflicting with doctor-patient confidentiality. This adds a unique layer of tension to a film that already has captivated a generation of thriller fans.

Relentless

Relentless cover
CinTel Films

Relentless tells the story of a rookie cop who recently transfers from Los Angeles to New York City. The cocky rookie (Leo Rossi) finds himself chasing a former cop who is now a disgruntled reject. The killer (Judd Nelson) picks his victims at random, and uses his expertise as former law enforcement to cover his tracks and make it difficult for the two partners to track his scent. Director William Lustig has many horror/thriller classics on his resume such as Maniac and several Maniac Cop sequels which inspired an HBO remake after a failed movie remake attempt in recent years. In this film, he sets the bar high and paves the way for Leo Rossi to star as Detective Sam Dietz in several sequels that were later released direct-to-video. In many cases, the original sets the tone for the entire series. This case is no different.