The antonyms for the word "invincibility" are vulnerability, weakness, and imbecility. Vulnerability refers to the state of being open to harm, injury, or attack, meaning that the opposite of invincibility would be a person or a thing with a significant susceptibility to harm or damage. Weakness, on the other hand, refers to the lack of physical or mental strength or power, indicating that the opposite of invincibility would be a person or a thing that is not strong or powerful. Imbecility refers to the quality of being stupid or mentally incompetent, so the opposite of invincibility, in this context, would be a person or a thing that is not intelligent or capable.