Ultra-strong is a term used to describe something that has an immense level of strength and durability. There are different ways to say ultra-strong, depending on the context and the intensity of the meaning. Some synonyms include invincible, indestructible, unbreakable, steadfast, robust, sturdy, armored, resilient, tenacious, rugged, and enduring. These words carry the same message as ultra-strong, but they also convey a unique aspect of strength that can be helpful in describing different situations. For instance, invincible may imply an unbeatable strength, while armored may denote protection from external forces. Overall, the synonyms for ultra-strong illustrate the different types of strength that exist in our world.