unfair
He unfairly punished all the children for the actions of a few.
They feel they are being unfairly treated.
I felt this article presented some issues unfairly.

SMART Vocabulary: related words and phrases

Unfairness and favouring someone unfairly
ableism
ableist
agism
agist
Anglocentric
discrimination
discriminative
discriminatorily
discriminatory
drumhead
one-sided
one-sidedly
one-sidedness
one-way
the old school tie
tokenize
two-tier
unbalance
unequal
unequally