Antonyms of adj preferential

1 sense of preferential

Sense 1
discriminatory, preferential -- (manifesting partiality; "a discriminatory tax"; "preferential tariff rates"; "preferential treatment"; "a preferential shop gives priority or advantage to union members in hiring or promoting")

INDIRECT (VIA advantageous) -> disadvantageous -- (constituting a disadvantage)

Similarity of adj preferential

1 sense of preferential

Sense 1
discriminatory, preferential -- (manifesting partiality; "a discriminatory tax"; "preferential tariff rates"; "preferential treatment"; "a preferential shop gives priority or advantage to union members in hiring or promoting")
       => advantageous (vs. disadvantageous) -- (giving an advantage; "a contract advantageous to our country"; "socially advantageous to entertain often")