The phrase "take one on" implies the idea of assuming responsibility or accepting a challenge. Antonyms for this phrase include "avoid," "decline," "refuse," and "resist." When encountering a complex task or challenge, some individuals may desire to evade the responsibility of completing it. Others may decline the opportunity to take on the challenge, either because they doubt their ability or because they have other priorities. Resisting the temptation to accept the challenge is an antonym for the phrase, as it shows a lack of willingness to step up to the plate. In essence, the opposite of "take one on" is the choice to sidestep or avoid taking on responsibility or challenges.