Antonyms for the term "stacks up against" can vary based on context, but they generally refer to to the notion of comparison or evaluation. Some possible antonyms of "stacks up against" include underperforms, fails, lags behind, falls short, pales in comparison, or doesn't measure up. Such antonyms highlight a lack of strength, inferiority, or weakness in comparison to a benchmark or standard. It may be useful to use such antonyms when describing situations where a product, service, or individual does not meet expected standards or fails to meet the expectations of others.