Disintegration is a fun way to start a story! Doc Savage in Murder Mirage and Mystery Under the Sea, with spoilers (#SFWApro)

Laurence Donovan’s MURDER MIRAGE is the third Doc Savage story to have someone disintegrated early on. However it’s closer to The Mystic Mullah: a story that features a mind-blowing, scene-stealing weapon but otherwise fairly straight.
Still, it’s a heck of a hook. The story opens with a freak summer snowstorm in New York, then cuts to a woman trying (as is usual in the openings) to reach Doc. When her car is cut off, she runs for it. A verdantly glowing green globe rolls down the street towards her, melting the snow for half a block. The woman disappears and in her place there’s a shadow burned into a nearby window.
If you guess the menace is radioactive, you’re right. It’s really striking how much it resembles the effects of an a-bomb, though without any explosive force.
Much of the early chapters involves Doc protecting the plate glass window (as in the William Baumhofer cover [all rights to current holder]) so he can analyze it; the bad guys want to smash it to make sure he can’t. A beautiful Englishwoman turns up and explains this ties in to a lost city her explorer brother found in the desert. After some run-ins with a crime-boss working on the bad guys’ side and some murderous Bedouins (stereotype time: Stalwart desert warriors, stone-cold killers, prone to yell about “the prophet” before they lop your head off), Doc, his aides and the Englishwoman are off to the lost desert city. The gang boss, having made sure his men look guilty as hell for the opening murder, informs them they either come along with him or let the cops fit them for a noose.
It also has Pat Savage, thoroughly loving every minute of being shot at or kidnapped, and the first of (IIRC) several stories where Doc shields his head with a bronze skullcap (his hair looks almost helmet like, so it’s an easy trick).

MYSTERY UNDER THE SEA (by Lester Dent, cover by James Bama, rights to current holder) opens with the most grotesque scene since The Annihilist. A sailor, “Twenty Thousand Leagues” Verne, tries to reach Doc. Rather than just kill him, the bad guys pour acid on his tongue, then slit his wrist tendons, so he can’t say or write the warning message. As it turns out, he’s able to make some markings with his feet once he arrives at Doc’s, though it takes a while to decipher them.
The bad guy is Captain Flamingo, a flamboyantly dressed seaman as crooked as they come. The not-so-bad adversary is “Diamond Eve” Post (the name was inspired by “Diamond Jim” Brady), a beautiful, diamond-dripping socialite. She’s not murderous or really criminal, just out for herself, and she knows that when Doc learns what the McGuffin is, he’s bound to want it to share it with the world. Eve wants to turn a profit. She seems to have wandered in from a 1930s movie about trouble-making socialites, fast-thinking, snark-spitting, ambitious but amiably so. And, of course, gorgeous.
The secret is a good one. First, Doc discovers the villains have a drug that enables them to live without breathing. That’s really handy as this issue’s lost city (abandoned and empty, unusually enough) is underwater. The oxygenating drug is just one of the amazing scientific wonders hidden down there, though it’s also the only one Doc is able to salvage from the explosive finish. Curiously, he sees it purely as a way for people with lung problems to live better and longer—that’s good, but isn’t the fact we can become mer-people somewhat more exciting? It felt like Dent forgot to add one of those paragraphs explaining why the drug is no big deal after all.