False Profits is easily the worst example. I don't think they broke the prime directive but it's ridiculous how the Ferengi managed to escape to their ship.
False Profits is worse than Threshold.
Janeway faked prophecy.
This would be the same as Harry dressing up as Jesus, materializing on centre stage of the Ed Sullivan Show 1966, upstaging the Beatles, claiming to be the second coming while using 24th century technology to fake a couple miracles, signalling that the end of days was finally over.
That would trigger some serious shit world wide as the lines of religious adversity conformed and waited for the second wave of rapture to grab them...
Janeway altered the development of that world removing those Ferengi cleverly just as easily as she had surreptitiously.