Here’s an odd thing – the technology that is really dangerous today all comes from the 1950s and earlier. The big inventions of the last 60 years are nowhere near as deadly as the ones from earlier, especially those from the first half of the 20th century. That period had the worst wars in human history, so maybe that’s not surprising. But what we see is that the really bad stuff from that period is almost all heavily regulated now. The worst problems of today are social, not technical.

Let me illustrate this by describing some tech that really harms a lot of people, and when it was developed:

Deliberately Dangerous Tech

• Sarin, the worst chemical weapon, was developed in 1939 in Germany but even the Nazis didn’t use it. It did get used by some of the most brutal regimes since then: Pinochet’s Chile, Saddam Hussein’s Iraq, and Bashar Assad’s Syria. It’s what the lunatic cult of Aum Shinrikiyo used to terrorize Tokyo in 1995. It’s 80 times more lethal than cyanide, and 500 times more than chlorine. The name comes from the initials of the last names of the chemists who created it, which is about the worst memorial ever. It is classified as a WMD and was outlawed by the UN Chemical Weapons Convention of 1997.
• Anthrax, the worst biological weapon, was used by Imperial Japan in China in the 1930s and weaponized by the UK in 1942, who poisoned Gruinard Island in Scotland with it. It has since mainly killed people who worked with it or near it. Outlawed by the Biological Weapons Convention in 1975.
• Nuclear Weapons, the highest energy weapons ever developed, in 1945 (fission) and 1949 (fusion) by the US. They have only been used once, at the end of WW II, because they’re useless for actual military purposes. The goal of war is domination, not destruction. Nuclear stockpiles peaked in the mid 1980s and are now down to 10% of previous levels. Desperate loser countries like North Korea still work on them, but no one else does, and their tritium triggers are actually decaying over time.
• Assault rifles, have killed more people in the last 50 years than any other weapon. They were introduced by Germany in 1944 as the SturmGewehr 44 because standard rifles were overpowered for typical engagements. What was needed was a high rate of fire, not accuracy at long ranges. The big breakthrough was in 1949 with the AK-47, a gun that worked in any condition. Ones have been found recently in Afghanistan that were made in 1953. It actually appears on the flag of Mozambique, and is one of the main legacies of the Soviet Union. They’re too widespread at this point for any kind of international control, although most countries have kept them out of civilian hands. Not the US, though, as is now demonstrated weekly.
• Cluster bombs, the worst kind of munition, since they kill over a wide range and leave lots of unexploded ordinance behind. This was yet another innovation of WW II, with versions from Germany, the US, and the USSR. Attempts have been made to outlaw them, but the major military powers, including the US, still use them regularly.

Then there is tech that was NOT deliberately designed to kill, but has caused a lot of damage even so:

Accidentally Dangerous Tech

• Leaded gasoline – has damaged IQs all over the world, and is likely responsible for the crime wave of the 1980s and 90s. Lead exposure harms neural development in children, and there is a distinct dropoff in crime about 20 years after lead is disallowed in fuel, when lead-free children mature. It was developed in the 1920s to permit cheaper fuel to burn cleanly in cars. It was disallowed in 1976 in the US, and in the 90s in Europe, but is still used in some places.
• Bisphenol A (BPA) – could be damaging human fertility, since it mimics the hormone estrogen and is an endocrine disruptor. Male sperm counts have dropped substantially in recent decades, and some associate that with BPA. It has distinct effects in mice studies, but the human studies have been too varied to settle on conclusions. It was first prepared in 1891 in Russia, and came into widespread use in the 1930s. It’s now used to make clear, tough polycarbonate plastics for things like water bottles, and in epoxy resins. Regulatory bodies in the US and Europe are just now recommending against its use, but environmentally-conscious consumers already avoid them.
• Chlorofluorocarbons (CFCs) – release free chlorine atoms when they’re hit by ultraviolet in the upper atmosphere, and the chlorines then catalyze the destruction of a lot of ozone (O₃). Since ozone is what mainly prevents UV from striking the surface, and UV is dangerous to all living things, this is highly bad. It wasn’t until the 1970s that Antarctic and satellite imagery could detect what was happening, and a treaty banning their use, the Montreal Protocol of 1976, was quickly put into place. It was a rare example of industry readily allowing regulation, and was made possible by the dire consequences of ozone depletion and the ready availability of substitutes.

So what recent technologies could be dangerous?

Possibly Dangerous New Tech

• Genetic engineering, could be used to make even more deadly plagues than anthrax. See James Tiptree’s story The Last Flight of Doctor Ain (1968), for an early and brilliant take on this. But superbugs have all the problems of nuclear weapons in terms of being indiscriminate and with uncontrollable side effects, and can’t even have targeted releases. They’re stupid as a weapon, and too difficult for terrorists to develop compared to much easier tech like sarin.
• AI, as in sentient machines that decide they don’t want to share the earth with us. The gleaming skeleton of the Terminator scared the dickens out of people, but I’ve never understood this trope. There isn’t a single self-reproducing machine on earth, and no one is working on them. All machines are made for some human purpose, not one of their own. Machines that do what they want are called industrial accidents, and are highly frowned upon. There is current computer software that is called AI by the nontechnical press because it mimics neural networks, but it doesn’t even appear to be changing productivity statistics, much less turning us all into serfs.
• Transhumanism, where people are enhanced by biological or machine methods to become oppressive overlords, the Red Skull trope. You only have to look at people with actual prosthetics to see how sad this is. They’re getting better, but are tragically far from even matching what normal bodies can do, much less exceeding them.

I do see a couple of things based on new technology that could be dangerous:

Likely Dangerous New Tech

• Omni-surveillance, which is now being used to oppress the Uighurs in the Xinjiang province of China. Cheap networked cameras and machine learning algorithms can keep track of millions of people without needing vast numbers of expensive human guards. A whole region can be turned into an open-air concentration camp. This appeared first in China because it’s a technically advanced country with few human rights, but can be replicated in a lot of places.
• Drone soldiers, both aerial and land-bound. Aerial drones were used a lot by ISIS in Syria to carry explosives. Legged robots are getting to the point where they really could replace people in breaking down doors and attacking settlements. The seminal work here is Forever Peace (1997) by Joe Haldeman, where drones allow the US to conduct Vietnam-like counter-insurgency all over the world without the US civilian population knowing or caring. They’re wildly expensive today, but tech that works always becomes cheaper and more widely available as it’s developed.

Anyway, what I see from these lists is that the really efficient means of killing were driven by the World Wars. A lot of tech with dangerous side-effects was developed in the Second Industrial Revolution of the early 20th century, when people were happy to just get things that worked, never mind the consequences. By the later 20th century, those consequences became much more apparent, and the tech was much more regulated. The Third Industrial Revolution of integrated circuits and computers, working medicines, and worldwide travel and shipping, has had far fewer bad effects.

The actual serious problems of today, like environmental damage, oppressive oligarchy, and the many kinds of discrimination, are not particularly technical. They’re mainly due to entrenched interests defending their income and privilege. Those are political and social issues, and much harder to change. We know how to fix the technical problems, and have done it in the past. Current tech trends will bring some new issues, but they pale compared to the political problems.