Determining the hardest sport physically is subjective and varies depending on the criteria used. However, according to several studies and rankings, boxing is often considered the hardest sport physically. It requires strength, power, endurance, agility, and the ability to overcome fear. Other sports that are often mentioned as being physically challenging include mixed martial arts, rugby, ice hockey, gymnastics, basketball, soccer, wrestling, water polo, and endurance sports like Ironman triathlons. It is important to note that each sport has its unique physical demands, and what may be challenging for one athlete may not be for another.