The term 'Relentless Pursuer' can be summed up by the crossword solution 'BLOODHOUND'. Bloodhounds are a breed of scent hound, originally bred for hunting deer and wild boar. They have an incredibly strong sense of smell, which makes them excellent tracking dogs. They are often used by law enforcement to track down criminals or missing persons. Bloodhounds are known for their tenacity and determination when it comes to tracking, making them the perfect choice for a 'Relentless Pursuer'.