There are several contenders for this title; the tank, the airplane, the crew-served machine gun, the flame thrower, and the submarine. However, I imagine that if I had been there, poison gas would have been the most frightening to me.
_______
It certainly seems that the gas was horrifying to those who lived through it, because after the war many nations got together and agreed not to use it again.
The nuclear bomb
Atomicbomb.
Probably artillery; it was responsible for many of the deaths in World War 1.
Yes. It was the best in the world.
The nastiest weapon used in the Viet War and by far the most feared weapon by the communist forces was the B52. The enemy could run or take cover from any weapon in the US arsenal; but not the B52. Arc Light missions were almost always conducted as a surprise to the enemy...there were hardly ever any previous warnings of an Arc Light mission; then when they came, they hit with monumental devastation.
It depends on what war you mean. Bombs, nuclear to be precise, were some of the most feared weapons. Tanks also were feared highly.
Hitler
Adolf Hitler
There can be no doubt that the most deadliest weapon of world war 2 was the nuclear bombs that dropped on Hiroshima.
Bismarck.
Georgy Zhukov .
the tank
Propaganda.
Mustard Gas
The most common one that was used as a weapon in World War 1 is called the Artillery
George Patton.
Most Americans, especially North Americans, feared the atom bomb and then the hydrogen bomb because our country, Russia and others were working hard to perfect the usage of that mass extinction weapon. People feared that someone would go crazy and push the button to launch the weapon and start World War III which would have lead to mass extinction of our species eventually. There are many today with the same fear.