unlike — different, dissimilar, or unequal; not alike: They contributed unlike sums to charity.
disproportion — lack of proportion; lack of proper relationship in size, number, etc.: architectural disproportions.
imbalance — the state or condition of lacking balance, as in proportion or distribution.
inequality — social or economic disparity: inequality between the rich and the poor; widening income inequality in America. unequal opportunity or treatment resulting from this disparity: inequality in healthcare and education.
unfairness — not fair; not conforming to approved standards, as of justice, honesty, or ethics: an unfair law; an unfair wage policy.
variation — the act, process, or accident of varying in condition, character, or degree: Prices are subject to variation.