set afire vs combust

set afire and combust both are verbs.

Word	Noun	Adjective	Verb	Adverb
set afire	No	No	Yes	No
combust	No	No	Yes	No

As verbs, combust is a hypernym of set afire; that is, combust is a word with a broader meaning than set afire:

Other hypernyms of set afire include burn.

set afire (verb)	combust (verb)
set fire to; cause to start burning	undergo combustion
	get very angry and fly into a rage
	cause to become violent or angry
	start to burn or burst into flames
	cause to burn or combust