The most severe of the degree of burns is the sixth degree burns which is worse because it involves the charring of bones.
The less severe of degree burns is the 1st degree burns that usually require no medical treatment but when you get into 2nd degree burns, 3rd degree burns, 4th degree burns and 5th degree burns those will require medical treatment and are severe.
But like I said the 6th degree burn is the worse burn which you do not want to get because it leads to charring of bones and could certainly even lead to death.