Not to Be Confused With the Band That Launched Peter Gabriel's Career
The Genesis Device is a convenient plot thread: a kind of bomb, developed by Federation scientists, intended to turn uninhabitable planets into bountiful gardens. Of course, if you launch it at a planet with people (or, you know, sentient aliens) on it, you're going to wipe out the whole planet in favor of recreating Eden.
The parallels to the atomic bomb are obvious. Like Dr. Marcus and her crew, the bomb's creators believed they were doing it for a greater good: ending the Second World War successfully. And like the Genesis Device, the atomic bomb became an apocalyptic weapon with the capacity to destroy a planet.
That might be why McCoy freaks out a little bit at Spock's dispassion over the whole thing:
MCCOY: Logic! My God, the man's talking about logic! We're talking about universal Armageddon!
So we've basically got a souped-up version of the A-bomb kicking around the galaxy and in danger of falling into the hands of a genetically engineered megalomaniac. It aptly demonstrates what the road to hell is paved with…and how good concepts sometimes turn into terrifying realities.
And there's a literary tradition that covers this too, though Star Trek II never makes direct reference to it. Once upon a time, there was a doctor named Victor, who had a great notion about how to bring the dead back to life. And hey, who doesn't want that? Turns out he created a monster who ended up running amok and destroying everything he held dear.
It's a pretty good story…much like The Wrath of Khan.