Most tightened can be described as the act of making something more secure or firm. The antonyms for this word include loosened, relaxed, or slackened. When something is loosened, it is made less tight, allowing for more movement or flexibility. Similarly, when something is relaxed, it is made less tense, allowing for a more natural state. Slackened refers to an object or material that is less tightly drawn, like a rope that has been slackened. These antonyms can be used to describe the opposite of most tightened, highlighting the change in the level of tension or security in a given situation or object.