wickedness vs foul play

wickedness and foul play both are nouns.

Word	Noun	Adjective	Verb	Adverb
wickedness	Yes	No	No	No
foul play	Yes	No	No	No

As nouns, foul play is a hyponym of wickedness; that is, foul play is a word with a more specific, narrower meaning than wickedness:

Other hyponyms of wickedness include devilry, deviltry, irreverence, violation, sexual immorality.

wickedness (noun)	foul play (noun)
morally objectionable behavior	unfair or dishonest behavior (especially involving violence)
the quality of being wicked
estrangement from god
the quality of being disgusting to the senses or emotions
absence of moral or spiritual values