警方正在全力追捕这名残忍的连环杀手。

The police are hunting down the brutal serial ___slayer with full force.

他是数学难题的杀手，总能轻松解决最复杂的题目。

He's a math problem ___slayer, always solving the toughest questions with ease.

这种新型杀虫剂被认为是蚊子的克星。

This new insecticide is considered a ___slayer of mosquitoes.