The science is flying fast and loose in here.
Professor Krauss' theories about a method for passing matter through matter were scorned and laughed at, so he turned them to crime, killing three and robbing the New York subtreasury*. Unfortunately for him he also gave an interview about his theories, which really helped research-savvy reporter Chic Carter track down and capture him. (Smash Comics 011, 1940)
*A Note on Subtreasuries: A frequent target for theft in the Golden Age or at least one that I've encountered 3-6 times, the New York Subtreasury was part of a US financial management system that distributed the storage of US gold reserves, but, critically, was phased out in 1920. I don't know what all these guys were after in there but there sure wasn't any gold.
Professor Abbot, disgraced former physics instructor at Stamton College, has developed a machine capable of paralyzing the population of a small city long enough for his men to rob it blind, but since the device also disrupts electrical signals this draws the attention of lineman Tom Dalton, aka Magno, the Magnetic Man. Abbot proves to be unusually well-prepared for the appearance of the local super-hero at his hideout and disables Magno with a prepared dose of knockout gas, which is really, really impressive, I have to say.
Abbot's downfall comes in the form of every villain's worst enemy, the deathtrap. Sure, slinging Magno down a well to slowly drown is satisfying, in an evil kind of way, but it introduces the possibility of him escaping from the trap, and if he does that then you are screwed. Just stab him with a wooden stake or something if you need to avoid using metal!
Anyway, Magno of course escapes from the trap and ends up blowing Abbot, his machine, his hideout and his gang to high heaven by the medium of some hastily smashed up mad science equipment. (Smash Comics 014, 1940)
This unnamed scientist does a bit of old-fashioned grave robbing in order to get only the finest parts for his frankenstein (though the fact that he made sure to include the brain of a scholar doesn't seem to have played out in the mentality of the creature) which he
then uses a growth hormone on and makes huge, super strong and bulletproof. Dubbed Brutus and deemed unstoppable, this creation is sent out to loot and plunder.
I always appreciate it when a character has to contend with a foe who is their rough equivalent from time to time - this is part of the appeal of Hellboy, for example - and Brutus offers just that opportunity for Bozo the Iron Man, being essentially a Bozo-shaped and-sized human of equivalent strength. Brutus manages to win the day in their first encounter by hitting Bozo over the head hard enough that Hugh Hazzard is knocked out through the armour of his robo-suit, but their second bout results in the deaths of both Brutus and his unnamed creator. (Smash Comics 014, 1940)
Across the US, buildings, trains, planes and ships begin sailing off into the sky, accompanied by a totally radical visual effect of a giant green mummy that I'm not 100% certain is actually visible to regular non-comic-reading witnesses - it's never commented on in any case, and if I saw a giant mummy carry a train off into the void I assure you that you would hear me speak of little else.
The culprit turns out to be one Doctor Robb, an unscrupulous archaeologist who murdered his colleague Professor Hill in order to steal an ancient artifact called the Power of Tutkamen (named after original owner Ra Tutkamen, natch).
Robb presumably refines his control over the power, as he seems to be using it to plunder passing shipping from his island base and that's hard to do if you're just blasting ships and planes into orbit. The party comes to an end once the Invisible Hood gets involved, as Robb discovers to his chagrin that having the power to levitate anything you see doesn't help you very much in a confrontation with an invisible guy. Rather than be captured, Robb does a header out the window of his lighthouse HQ. (Smash Comics 016, 1940)