The phrase "went belly up" means something failed or went bankrupt. The antonyms for this phrase could be 'succeeded', 'prospered', or 'throve'. If something 'succeeded', it means it achieved its goals or objectives. If something 'prospered', it means it experienced growth and prosperity. If something 'throve', it means it flourished or thrived in a particular environment. These antonyms offer a positive contrast to the negative connotations of "went belly up". They suggest that the subject of the sentence is doing well and thriving, rather than failing or struggling. These antonyms are helpful in painting a more optimistic picture of a person, business, or institution.