Other candidates I considered for this list:
* Swarm robotics (kinda covered by drones)
* 5G (not for the dumb conspiracy reasons)
* Quantum computing and other potentially transformative computing advances
* VR/AR
* Laser weapons
* Ballistic missile defense
* Stealth technology
* Hypersonic missiles
* Cryptocurrency
Most of these simply don't provide the cornucopia of terrifying potential applications of the 4 I picked.
There's plenty of terrifying non-emerging technologies too.