Antonyms of adj opportunistic

1 sense of opportunistic

Sense 1
opportunist, opportunistic, timeserving -- (taking immediate advantage, often unethically, of any circumstance of possible benefit)

INDIRECT (VIA expedient) -> inexpedient -- (not suitable or advisable; "an inexpedient tactic")

Similarity of adj opportunistic

1 sense of opportunistic

Sense 1
opportunist, opportunistic, timeserving -- (taking immediate advantage, often unethically, of any circumstance of possible benefit)
       => expedient (vs. inexpedient) -- (serving to promote your interest; "was merciful only when mercy was expedient")