Complex sentence: Many of these slashers were "Halloween" imitators, reusing the simple template of teens being stalked by a murderous figure, which filmmakers put their own spin on, with varying degrees of success.
Split into simpler sentences: Many of these slashers were "Halloween" imitators. They would reuse the simple template of teens being stalked by a murderous figure and allow the filmmakers to put their own spin on the premise, with varying degrees of success.