That's why you don't take out an entire species with a nuke. Too many margins for error. You do what Shyamalan did. You engineer a neurotoxin specifically designed for your target. Then you wipe them all out. That's what JARVIS learned from watching Terminator.

[ It's possible he wouldn't sound quite so proud of his AI if he thought there was even a remote possibility that JARVIS would go Skynet on the world. But he knows he won't. ]

Plasma guns? Really? I made something like that once. Prototype. Never really took off. Military was too attacked to bullets.

And I say, make it fun.