Worst hand gun recoil I have dealt with was an older AOW side by side that was called the "backup" or some such, Essentially a 8 inch 12 gauge SXS. the pistol grip was like the long tang round knob superposed style, except there was no butt stock. Even as a rough and tough 24 year old, that dang thing HURT> flexing the wrist several hours later was enough to cause tears.
A 5 shot .475 linebuagh blackhawk conversion might be the worst "conventional" handgun I have fired, It had the Bisley grip frame and that just does not fit me.
Worst recoiling gun I have fired was simply a matter of fit.
My brother works for a very affluent man who hunts world wide. He decided that for his 60th b-day he wanted to get a custom made 338 SXS double rifle from Merkel. He's a shorter barrel chested guy and he went to Germany twice to have the gun fitted. I have watched him with the gun and he has hit a bowling ball rolling across the grass field twice almost as fast as you can say it. I was offered the chance to shoot it and "hey, who turns down a chance to shoot a $70,000 gun?" Well, I shot one time at the gong, at the shot, my nose was swelling, my glasses were sitting on the over lever and my face felt like I had been punched. When you raised the gun it felt like a perfect .410, pointed where you looked, but it was made with about a 12 inch pull, a little more dropoff than I would have had, and with his "round" face, the top of the stock was much thinner than what I would have. It was like shooting a 5 pound .410 game gun only loaded with 1 7/8 ounce lube 2's. I only fired it once.
That said, I have fired a half a box of .460 wby with no discomfort when standing up, and maybe ten rounds of .416 rigby from the bench with a Westley Richards square bridge Mauser and been just fine. (the Westley Richards .425 is just the same, but it also brings back why the Great White Hunter used a gun bearer, its a beast, maybe 11 pounds empty with no sling.)