Damn this thread is funny!
My worst is actually an innocent looking sub-nose rovolver. A 10oz scandium frame titanium cylinder S&W .357 shooting full load 125g Federal Hydroshoks. My buddy and I have cleared many a gun range popping off that monster. Most I have gone is five rounds with a bloody web and a serious flinch after the first round.
There was a guy in my CCW class who showed up with one of those, & the instructors started teasing him immediately - as in, the day before
we had to qualify. He didn't finish his first round of shooting before he begged them to let him trade-out for his 9mm. They were most gracious, and allowed it.
I have a buddy who had a small-frame S&W .357 with small wooden grips. Quite pretty, they were, but the edges were squared-off enough that they cut the crap out of my hands after only 3 rounds.
Even a properly weighted handgun can't overcome tons of powder. I fired 2 rounds from a guy's Desert Eagle, & handed it back to him. I hit exactly where I was aiming, but my hands, wrists, elbows, arms, and shoulders were shaking, and I think I may have had a small "kiss" from the hammer... in my forehead...