antagonistic, incompatible -- (used especially of drugs or muscles that counteract or neutralize each other's effect)
uncongenial, incompatible -- (not suitable to your tastes or needs; "the uncongenial roommates were always fighting"; "the task was uncongenial to one sensitive to rebuffs")
incompatible -- (incapable of being used with or connected to other devices or components without modification)
contrastive, incompatible -- (of words so related that one contrasts with the other; "`rich' and `hard-up' are contrastive terms")