Plate armor is your best bet. Padding helps, which was worn under chain. The padded garment worn under chainmail is called gambeson. Gambeson would help, but it wasn’t close to perfect. Put on a dense, thick puffy coat and have someone hit you with a steel baseball bat as if they were trying to kill you. You’ll feel it. Plate armor is the best choice. Obviously with enough blows from a hammer or mace and it could cave in and crush you, but that was rare. Best way to kill a knight in full plate was to get a few of your friends, pile on him, and put a dagger in the gaps of the armor. Throat, thighs, groin, anywhere there would be gaps in the armor.