Whomever is the object form of 'whoever' - used when the word is the object of a verb or comes after a preposition, following the same rule as 'him/her' instead of 'he/she.' For example: 'Give it to whomever you like' (object of 'to'). In real, everyday English, especially spoken English, many people just use 'whoever' in both places, and 'whomever' is starting to sound quite formal or even old-fashioned to some ears.

(受格)無論是誰、任何人