What is the opposite of being 'disinterested'?

Being 'disinterested' refers to a lack of bias or personal stake in a matter; it implies impartiality. Therefore, the opposite of disinterested is 'biased,' which means having a preference, leaning, or preconception that affects judgment. When someone is biased, their perspectives may not be fair or objective, in direct contrast to the disinterested state.

The other choices do not convey the opposite meaning effectively. 'Complacent' refers to self-satisfaction, often without awareness of potential dangers or deficiencies. 'Indifferent' suggests a lack of interest or concern, which aligns with a disinterested state rather than contrasting it. 'Neutral' implies a position of not taking sides, which is closer to being disinterested than its opposite. Thus, 'biased' stands out as the choice that embodies the opposite of being disinterested.