The IF's highest showings vs adamantium's highest showings?
Can't say, but I have my doubts he'd do any thing. IIRC, Thor once threw Mjolnir as hard as he could at a block of adamantium and only made a small dent in it.
I doubt it'd harm first grade Adamantium. True Adamantium is really the only constant in the Marvel U. Nothing has really ever been shown to be strong enough to physically harm it by breaking or bending.
Doubt that Iron Fist could harm true adamantium. Etc. Namor punched an robot made out of true adamantium and didn't hurt it...and I rate Namor's highest punches far above Iron Fist's...
i'd say danny's uppermost limit would be akin to namor on a good day. not on his best day, considering some evidences that suggest he's just a ****ing bulldog of destruction when he wants to be, but certainly danny at least hits namor's average.