The phrase "going phfft" describes something that is fizzling out, dying down, or losing momentum. Some antonyms for this phrase could include "flourishing," "thriving," "growing," or "succeeding." When something is going phfft, it is often associated with failure or disappointment, so the opposite of this could be "succeeding," "achieving," or "prospering." Additionally, words like "booming," "rising," "surging," or "expanding" could also serve as antonyms for "going phfft," as they describe situations where something is experiencing significant growth and momentum. In general, the antonyms for "going phfft" are words that convey positivity, success, and progress.