thug vs felon

thug and felon both are nouns.

Word	Noun	Adjective	Verb	Adverb
thug	Yes	No	Yes	No
felon	Yes	No	No	No

As nouns, felon is a hypernym of thug; that is, felon is a word with a broader meaning than thug:

thug: an aggressive and violent young criminal
felon: someone who has committed a crime or has been legally convicted of a crime

Other hypernyms of thug include criminal, crook, malefactor, outlaw.

thug (noun)	felon (noun)
an aggressive and violent young criminal	someone who has committed a crime or has been legally convicted of a crime
	a purulent infection at the end of a finger or toe in the area surrounding the nail

thug (verb)	felon (verb)
Acting like a criminal or antisocially but with positive connotations