There's no single answer to the question of which state has the fewest required high school credits for graduation. State requirements vary significantly, and the number of credits isn't always the best measure. Some states specify credits in different ways (e.g., Carnegie units, which represent a specific amount of instructional time, vs. simply a number of credits without specifying the time commitment). Furthermore, some states allow for alternative pathways to graduation that don't strictly adhere to a credit-based system.
To find the specific minimum credit requirements for a particular state, you would need to consult that state's department of education website.