Extra strong is a common phrase used to describe something with exceptional durability or power, but there are many other ways to convey this idea. Some synonyms for extra strong include robust, sturdy, resilient, tough, powerful, unyielding, and steadfast. These words can be used to describe physical objects like buildings, machinery, or materials, as well as abstract concepts like willpower or emotions. Using precise and varied language can add depth and nuance to your writing, making it more engaging and effective. So whether you're tackling a tough project or describing a person's strength of character, don't be afraid to explore the many synonyms for extra strong at your disposal.