One of his main techniques is biting, and he can bite hard enough to easily crush wood with his teeth. He claim that his teeth can tear a coconut. Although he lost all of his teeth, his bite can still damage Izou Motobe when he wear a chain mail made of aramid fibers, which is made for plane and tire. His body is strong enough to surpass drugs, even though he used abnormal amount of drugs. His strength is shown many time in the story: defeating the convict Sikorsky in a telephone box and withstanding his knuckle slash in the underground arena, taking many blows from Mohammad Alai Jr and defeating him, cutting his tongue in the process, fighting with Pickle and making him run away in fear of the only creature that scare him: a wasp. Despite of using brute force to fight, Jack is very tactical and smart enough to counter his opponents. For example, he found the weakness of Aiki after being throw many times and used a similar move to defeat Goki Shibukawa .