Unequal means not the same in size, rank or fairness. Unequal treatment, an unequal struggle, unequal to the task.
Unequal to something is a separate use meaning not able to manage it, and it is a polite way of saying somebody could not cope. An unequal struggle is one where the sides were never matched.
1adjectiveunequalNot the same in size, rank or fairness.
“The two teams were unequal in size, so we moved two players across.”
unequal is a quality.
Un-, not, plus equal, from Latin aequalis, from aequus, level.
Middle English
unequale
English, today
unequal
From Middle English unequale, equivalent to un- + equal. Compare German unegal (“unlevel, uneven”).
Etymology from Wiktionary, CC BY-SA