600 Nitro Express
Not even close. There are several more powerful handgun cartridges, not counting the single shot pistols that use rifle cartridges. While Dirty Harry may have proclaimed it to be "The most powerful handgun in the world"- it is not.
Factory, I'd probably say the 500 Magnum
M2 can be hand held, but, that is the exception. MP5 in 10mm is along the lines of what you might be asking about.
Other than a toy gun or water gun, the next most powerful one a citizen can have without a permit is a "B.B. gun".
yes but it wont be as powerful
50 cal. machine gun. i don't know who decided to use it.
Air rilfes have been made that will take down large game.
577 T Rex
star cannon
Most likely a RG.
The magnum .55 is the most powerful, but some Desert Eagle has the highest calibre bullet.
Wood