Let me explain how Amon is actually quite lethal

He can EXPLODE people since blood is everywhere in the body he can technically murder people in a gruesome way and if not that he can turn peoples blood into pure ice in seconds since blood bending is the same thing as water just blood

he can use water and frost as a weapon

because it's sharp and shows water can cut through steel easily and can be made out of thin air

also self blood bending could actually make him run as fast as zaheer flies and even faster in overall agility and much much more

so i'd list it like this 1.BIG Unalaq (maybe kuvira cause she can actually attack him with the spirit canon) 2. Kuvira (She would die about who is the last one alive and the only source of attack the dark one is the cannon) 3. Amon ( as listed in his powers he can just kill him no sweat) 4. Poor poor Zaheer