pursuer
Definitions
A person or animal that follows someone or something in order to catch or attack them.
Someone who actively seeks to attain, achieve, or engage in a particular goal or activity.
Examples
The exhausted runner glanced over his shoulder to gauge the distance between him and his relentless pursuer.
By taking a sharp turn into the narrow alleyway, she managed to lose her persistent pursuer.
The detective felt like a hunter closing in on his prey, but he was unaware that he had become the pursuer of a dangerous criminal.