Lowballing. To assume Sub-Relativistic would be to assume that Ying did in fact run to the South Pole and back within the time frame that we do not see her. Unfortunately, that's not something we can assume without any other feat of her being Sub-Relativistic to back it up.
well the current feats i know besides the one in the latest movie is that he caused a volcanic eruption that would cover hundreds of miles on planet volkania when he launched the tumbukan berapi at fang , sai and shielda in a fit of rage while using boboiboy api and he is inorganic when he splits into ,2 ,3 ,5 or 7 bodies
actually wasnt there that one time where Probe could oneshot an amped coco jumbo that has a body as dense as diamonds while being massive at the same time which boboiboy could scale to since he one shotted probe when he was boboiboy fire