The word "chin-up" can have a few different meanings, such as physical exercise or perseverance through difficult times. As such, its antonyms can vary depending on the intended meaning.
For the physical exercise, a possible antonym could be "couch potato" or "sedentary," indicating a lack of physical activity.
As for perseverance, antonyms could include "defeatist" or "resigned," implying a lack of motivation to overcome challenges. "Giving up" or "quitting" could also be considered antonyms, as they represent a failure to persevere.
Essentially, whatever term denotes the opposite of "rising to the challenge" or "persevering through adversity" could be considered an antonym for "chin-up.