In this corner, we see bitter widower Frank Castle, the original scourge of the underworld, the guy who can pull off the skull T-shirt garb and not look like a huge dork, The Punisher. In the other corner, a more mysterious figure in a red scarf, floppy hat, and black cloak: playboy Lamont Cranston, a.k.a. Kent Allard, a.k.a. The Shadow. And remember, The Shadow knows what evil lurks in the hearts of men.
Now, both these fellows hate crime with a passion, and share a fondness for spreading fear and general mayhem among the criminal element with big loud guns. Normally, I'm sure they'd love to meet one another, and spend hours over a couple of beers (or possibly ginger ale, to keep sharp --- is Frank a straight-edge?) swapping war stories, shooting the breeze, and just generally talking shop. They'd share such tips as how best to hamstring a thug, or where exactly to knife a mobster for maximum bleed time. Yes, under normal circumstances they'd get along like a cathouse on fire.
However, this is a fight, not some ladies' social club, so less chat, more splat. Assuming neither party has the advantage of an ambush, each of these two would, at first, have a pretty even chance of taking the other out with a single bullet. And both are fair shots with a firearm.
Now, Frank's seen a lot of combat, but the Shadow has been fighting the good fight for going on five decades, as some writers have it. He may in fact be ageless. And the Shadow is not only a more experienced and nuanced strategist than Frank, he has been known to turn invisible (save only his shadow... spooky), and has the power to "cloud men's minds." He's got an extremely strong, mass hypnosis-inducing power, to be precise. It wouldn't be long before he was counseling poor, post-traumatic stress disorder-sufferin' Frank to eat his own gun --- and Frank would be happily complying.
Next: You just opened up a whole snikt-pack of trouble!