@juanan The average 12-year old male child is capable of breaking down an average sheet-wood interior door with his bare hands and effectively no training; either by shattering the wood enough to open a hole, or by ripping it off the hinges/socket. Cracking open the back plate of a steel cuirass is a bit too much "anime emphasis", but it's feasible that a naturally large, strong man who obsessively trains for it could dent the front plate of said steel cuirass enough to break the ribs and compress the torso into breathlessness.
The vast majority of what people consider physically possible has no relation to what is actually physically possible; it's inexperience and fear of hurting yourself in the process. That's why most real martial arts put so much empahsis on technique > power > speed and techniques for mitigating damage (rolling with the strike, slapping out, etc)
@dodayme Maybe; it's hard to tell because of the anime-action-blur. This is actually a legitimate anti-blade fighting technique; any instructor will tell you that, 95% of the time, getting into a knife / sword-fight with your bare hands means you will get cut so it's important to mitigate the damage. One of the most common methods is to turn your arm so that the blade strikes the "top" of your upper arm - this ensures that the major veins and closing tendons on the inside aren't hurt. It would have been better and more historically accurate if Karate Idiot had taken off his
gi top and wrapped it around his left arm.