Not a medieval weapon, but developed earlier. It burned so fiercely that it burned under water. “The secret behind the Greek fire was handed down from one emperor to the next for centuries. read more
Modern tanks have armor <500mm due to composite armor, nothing in WWII and before could penetrate or kill the tank (assuming we are talking about Tank vs. Tank). The best the enemy could do would be to immobilize it with anti-tank mines. read more
Medieval knights in steel armour could be killed or maimed by being hit on the head with a war-hammer - a more modern version of a club. The war hammer was often mounted on the end of a pole and was sometimes mixed with other nasty spikes/spears etc on the end of the pole. read more