Stonefish from Most Venomous Animal
Perhaps Stonefish could not win a beauty contest, but it could win award for being most poisonous fish on earth. Its venom leads to such a serious pain that the victims of its bite want the affected limb to be amputated. It is explained as the worst pain known to man. It is attended with potential shock, paralysis, and death. If you're not given medical care within a pair of hours you will be dead.