The correctly spelled word is "MALODOROUS." It means having an unpleasant or foul smell.

Explanation of the other options:

☀ HEIRARCHY: The correct spelling is "HIERARCHY," which refers to a system of organizing or ranking things or people.

☀ APPAULLING: The correct spelling is "APPALLING," which means causing shock, horror, or dismay.

☀ PESTILLENTIAL: The correct spelling is "PESTILENTIAL," which means relating to or causing a contagious or infectious disease.