Steadfast means firm and unmoving in support, whatever comes. Loyal, and still there afterwards.
It is a compliment and a warm one, and it attaches to support, refusal and friendship, so a steadfast ally and a steadfast refusal are both admiring. The word is formal and slightly old-fashioned, which suits its subject. The adverb steadfastly usually attaches to refused. Unwavering does the same job, and both are about holding a position rather than about strength.
1adjectivesteadfastFirmly loyal or unwavering in purpose.
“She was steadfast in her support throughout.”
Also accepted in games: unwavering, loyal
Proto-Indo-European
*steh₂-
Proto-Germanic
*stadifastuz
Old English
stedefæst
Middle English
stedefast
English, today
steadfast
From Middle English stedefast, from Old English stedefæst, from Proto-Germanic stadifastuz, equivalent to stead + fast. Cognate with Middle Dutch stedevast (“steadfast”), Icelandic staðfestur (“steadfast”), Danish stedfast (“firmly attached, secured”), Danish stadfæste (“to confirm; ratify”), Norwegian Nynorsk stadfesta (“confirm, ratify; establish”), Swedish stadfästa (“to confirm; establish”).
Etymology from Wiktionary, CC BY-SA