biased
Favoring one side unfairly instead of being fair.
To be biased means to favor one side unfairly, letting your preferences cloud your judgment instead of looking at things objectively. When a referee is biased toward the home team, they might call fouls more harshly against visitors. When a teacher is biased against a certain student, they might grade that student's work more critically than others, even when the quality is the same.
Everyone has natural preferences and opinions, but bias becomes a problem when it prevents fair treatment or clear thinking. A biased news article might present only facts that support one political view while ignoring important information that contradicts it. A biased judge at a science fair might favor their own child's project regardless of its actual merit.
Being unbiased means striving to be fair and objective, considering all sides before forming an opinion. While perfect objectivity is probably impossible (we all have experiences that shape how we see things), recognizing our own biases helps us make fairer decisions and see situations more clearly.