disadvantageous

dis|ad|van|ta|geous /d'ɪs'ædvənt'eɪdʒəs/
[ADJ] oft ADJ to/for n
Something that is disadvantageous to you puts you in a worse position than other people.
The Second World War started in the most disadvantageous possible way for the western powers.
= unfavourable
≠ advantageous