The antonyms for the word "more strengthening" can be words like weakening, reducing, decreasing, limiting, impairing, enervating, debilitating, and enfeebling. While strengthening implies an increase in power, vigor, or resilience, these antonyms imply a decrease or loss of these qualities. For instance, a weakening of the muscles, reducing of the immunity, and enervating of the mind. There could be many reasons why something loses strength, whether it's due to illness, injury, age, or neglect. However, it's important to identify the cause of weakness and take steps to address it, such as exercise, proper nutrition, and rest.