1. causing severe physical or mental pain; extremely distressing or difficult to endure
Usage: British spelling (American: agonizing); commonly used to describe emotional or physical suffering
2. causing worry or anxiety; making a decision or situation very difficult
Usage: often used in contexts of uncertainty or difficult choices

Examples

• She suffered an agonising headache that lasted for hours.
• The agonising wait for test results left him anxious and stressed.
• It was an agonising decision to leave her job after ten years.
• The patient described agonising pain in her lower back.
• The team faced an agonising defeat in the final seconds of the match.
• He endured an agonising period of uncertainty about his future.
• The agonising loss of her pet was difficult for the entire family.