"More than one can stomach" is an idiom that means something is so unpleasant or distasteful that it makes one feel nauseous. If you wish to describe this feeling using synonyms, here are some suggestions: too much to handle, overwhelming, excessively repugnant, intolerable, sickening, revolting, nauseating, disgusting, loathsome, abhorrent, repulsive, offensive, off-putting, and repellant. These synonyms can be used interchangeably depending on the context of the sentence. However, regardless of which synonym you use, it is clear that the idea conveyed is that the situation or object discussed is too much to bear.