The phrase "going great guns" means that something is going extremely well. Antonyms for this phrase could be "struggling," "failing," or "stagnating." These words indicate that the situation is not going well and that there may be obstacles in the way. Other antonyms could include "sluggish," "lackluster," "unmotivated," or "uninspired." These words suggest that the performance or progress of something is lacking energy or excitement. Overall, the antonyms for "going great guns" convey a negative tone and imply that something is not achieving its full potential or experiencing success.