step in vs supersede

step in and supersede both are verbs.

Word	Noun	Adjective	Verb	Adverb
step in	No	No	Yes	No
supersede	No	No	Yes	No

As verbs, supersede is a hypernym of step in; that is, supersede is a word with a broader meaning than step in:

Other hypernyms of step in include replace, supervene upon, supplant.

step in (verb)	supersede (verb)
get involved, so as to alter or hinder an action, or through force or threat of force	take the place or move into the position of
act as a substitute