I see at least 80 skill descriptions matching the word "guaranteed", like here is one example that Bamiji added over two years ago for m!AS Isuka's All Equal skill on Feb. 25 2021. Edit: I just noticed that Bamiji also uses it on the wiki tier list & Evaluations/Ratings pages OFTEN - e.g. ES Tsukiha:
>If present in the frontline at battle starts, inflicts 5-turn guaranteed Pain on all enemies.
On (the predecessor to) this page, Vivilerie was the first one to add that language, though in fairness my original 2 categories were "ignore enemy resistance" vs. "not guaranteed", which while technically correct did set the stage to take it that one step further to the more ambiguous version, which is why I am now advocating that we avoid using the word entirely in skill texts even in the negative sense. Because as you said: it ignores resistance, but it does not ignore barriers, nor those particular enemies who can never be afflicted with it, plus when not a fixed turn, it can be cured in the next turn, so it is not "guaranteed" aka "assured" at all.