det·ri·men·tal
ˌdetrəˈmen(t)l/
adjective
tending to cause harm.
"releasing the documents would be detrimental to national security"
synonyms: harmful, damaging, injurious, hurtful, inimical, deleterious, destructive, ruinous, disastrous, bad, malign, adverse, undesirable, unfavorable, unfortunate