oh right, and third: He wasn't told about the condition till she only had like 4 hours left to live if she hadn't fought him. There was nothing he could have done in 4 hours that would have saved her, even with his newfound power, that, more than likely he'd end up killing her with anyway if he tried helping by infusing Ki or something. And it'd take way more than 4 hours to find some cure or some sh**. Plus, his power is still too great to be used for long lengths of time.