Bring knowledge of CFCs to a time when we’re able to make them but not able to detect the ozone problems they cause.

The thing here is that I have zero desire to screw people over.

Hmm I don’t know. Probably go back to Germany 1940 and give them all the information needed to develop nuclear weapons first. You just know that Hitler would’ve pushed the red button a hundred times over if he had the chance.

Procrastinate, the world is going down the drain just fine without my help.

Give the ancient civilization ruled by the most evil ruler modern weaponry and explain how it works

Go back to the Garden of Eden with a bucket, grab all the apples, then head back.

Buy a cheap pistol, go back in time, and shoot Gutenberg.

We’d still be living in medieval times.

I’m heading far into the future - say 1000 years or perhaps 100 if communication would be an issue. I’m going to grab all sorts of portable devices and tools to take back with me, and I will maintain the remainder of my life without sharing my goodies. The world is screwed because they get no fruits of my intense labor, but that is fine since I hate them anyway. For that afternoon of work, I get to live a great life while everyone else must suffer in modernity.

How much power do I have?

If I could divert the asteroid that resulted in the K-T event, that’d drastically change history. It may not have stopped dinosaurs from eventually going extinct, but it’d have given them 33 million more years more to evolve, and would certainly have affected mammalian evolutionary history. Maybe, just maybe, raptors would have gotten smart enough.

Ooh! Take back a lot of ravens. They’re almost smart enough already. Heck, I wonder if taking ravens back even earlier would be enough for them to evolve into something dominant. Problem is, they’re not particularly social, and I think that’s been our greatest advantage.

Or: introduce modern octopus to ancient oceans.

Stopping the K-T event is my favorite, though. It would absolutely have changed how life on Earth has evolved since.

30M years between extinction events is about all you get, though.

Can I appear anywhere? Pop into white house or Kremlin during the Cuban missile crisis and say: I’m from the future, you must attack, or… Then travel back to the future without finishing the sentence.

If I ever got sick from something like COVID, I’d just go back to medieval Europe and let it spread like wildfire. I guarantee this modern disease would absolutely wipe out a large majority of Europe and everywhere else it spreads in the world. And little to no effort besides waiting for if I ever get it (which I thankfully never have had and hope I never will).

Shoot Arch Duke Ferdinand. Few people even now about it today, but he was subject to a horribly mangled assassination attempt that many scholars belive would have set off a major war in Europe had he died.

My name is Friedrich Trump (aka Frederick Trump) and I already did that and even had a nice hump.

You’re going to pretend we’re not on that timeline right now? I see your play, time traveller.