Dexter
This report covers the full original run of Dexter (Seasons 1-8, 2006-2013). A prestige crime drama in which a Miami forensics expert leads a secret life as a vigilante serial killer; it is consistently graphic and tonally dark across all eight seasons.
Episodes to know about
Blood-spatter imagery, crime-scene corpses, and Dexter's kill ritual (wrapping victims in plastic, using a blade) are present from the pilot onward and are a baseline feature of almost every episode.
Season 1's antagonist (the Ice Truck Killer) leaves dismembered, bloodless bodies arranged as crime scenes; severed limbs and limb displays recur throughout the season.
The Trinity Killer is shown physically and psychologically abusing his wife and children repeatedly across the season to force their obedience.