The most powerful cartridge developed specifically for civilian use would be the .585 Nyati.
us
There is no most powerful airsoft sniper rifle that you can just buy. But, Iv'e heard of guys tuning them over 800fps with custom parts. My most powerful is 600fps.
Eminent Tech TRW 17 is the worlds most powerful subwoofer.
United States Military
the most powerfull locomotive is soviet 2TE126
You will have to elaborate. Custom? Factory? Historicaly associated?
The United States of America China
500,000 euros
First, it is rifle, not riffle. Second, no, or we would shoot tanks with a rifle. Cannon are more powerful. Finally, depends on the rifle. I have a .22 rifle and a .44 magnum pistol. The pistol is far more powerful than the rifle. I also have a .22 pistol, and a 30-06 rifle. The rifle is far more powerful than the pistol (in THAT example).
.950 J D Jones
Anzio Iron Works 20mm
Jennifer Lopez.