Inflexibly rhymes with:
flexibly, flexibly, flexibly, flexibly, flexibly, forcibly, impossibly, inadmissibly, irresponsibly, irreversibly, noticeably, ostensibly, passably, peaceably, possibly, responsibly, sensibly
Inflexibly sounds like:
implacable, implausible, implausibly, impulsively, inapplicable, inflexible