It's most certainly NOT the atomic bombs.
Between the two bombs dropped on Japan, there were likely considerably less than 300,000 casualties. This is a terrible number of people killed and in pain, but it pales in comparison to the 50,000,000 killed worldwide during the war, with as many as half of those being Russians.
There may not be any hard and fast answer to this, but some good guesses would be certain German small arms such as the MG-34, or MG-42 machine guns, the MP-40 submachine gun, or the standard infantry rifle Mauser k98, which saw action in both world wars.
The british Lee-Enfield saw action in both wars as well.
It was the use of Poisonous Gas Oh no it was not ! No poison gas in WW2 (Except 1 minor event in Bari harbour in Italy.) The Atom bombs killed the most people in 2 single detonations. Most people to die would be on the Eastern front, Soviet Russia, but what kills them may well be starvation & disease as well as military means. I am thinking most people die of a single cause will be the civillian population of Germany due to allied aerial bombing, but I am sure the actual causes of death are probably unquantifyable.... Ahh sorry, poison gas as in Concentration camps..... Hmmm, I do not know.
Either artillery, machine guns, or the rifles and bayonets of common soldiers.
The atom bomb.
or the apache helicopter, its a matter of opinion.
The nuclear bomb
Atomicbomb.
Probably artillery; it was responsible for many of the deaths in World War 1.
8 million horses were killed in world war 1
Big guns (i.e. artillery, not hand weapons).
The 30.cal machine gun.
Yes, it killed many people.
There can be no doubt that the most deadliest weapon of world war 2 was the nuclear bombs that dropped on Hiroshima.
the tank
Mustard Gas
Propaganda.
The most common one that was used as a weapon in World War 1 is called the Artillery
The most common method was with artillery.It is NOT a biological weapon, it is a chemical weapon.
The Atomic bomb.
The A-bomb.
The nuclear bomb
Atomicbomb.