Doesn’t matter what era.

First, before using the death note, publish everything you know about the future and its tech. For example, even if you barely remember the periodic table, filling out anything you remember about it would significantly expand humanity’s understandimg at the time. Describing protons, neutrons, electrons, photons, quarks, positrons, neutrinos, bosons, etc would be a century or more ahead of its time. Knowing about radiation at all would save tens of thousands of lives from suffering just from avoidable exposure deaths.

Any modern common knowledge about germ theory, DNA, cell biology, virus structure, or the idea of antibiotics would be revolutions at the time. Just knowing penicillin comes from mold would save millions of lives, not to mention the isolation of stuff like insulin.

Asserting the existence of the photoelectric effect (photodiodes, solar panels), piezoelectric effect (phone haptics, timing crystals), the thermoelectric effect (any digital thermometer), and remembering that computer chips have something to do with silicon puts us ahead 100 years technologically. Knowing the best batteries are made mostly of lithium and something else puts us 100 years ahead in battery tech.

Knowing that rubber is supposed to be black leads to the discovery of vulcanization early and saves us from decimating the whale populations.

Knowing there are massive oil deposits in the middle east, Texas, Canada, and Mexico, or massive gold/diamond/steel/copper deposits in various areas makes nations supremely wealthy instantly after they extract resources.

For our purposes, though, photography need to advance drastically. If you know this is coming and have time to prep ahead of time, you learn everything you can to hasten the invention of the photograph.

Then you get to work with the death note.

In general: you start eliminating the elite class in whatever country you’re in. Slowly, so as not to create a power vacuum that destabilizes the nation.

Because of your scientific predictions that keep coming true, elites keep wanting to meet you to see if you can make them richer. That’s how you gather catalogs of faces.

Once your country moves to a strong collectivist government (socialist, communist, whatever) whose officials are chosen by true random sortition, you move on to the next one. Obviously you may have to do things out of order if there’s an imperialist military threat to your country, but that’s the idea. Keep society invested in the sciences and engineering to advance living conditions for all.

I’m in the US, so I’d focus on the immediate halt of the slaughter of native Americans. Oregon is already a state, so we’d still likely pick up idaho and Wyoming.

That’d probably result in an independent nation of natives in California, arizona, New Mexico, and Oklahoma. Oklahoma absorbs the Texas panhandle as a result.

A separate native nation forms in the Dakotas and Montana.

I’m not sure of statehood sentiment after that; it’s likely the Dakotas/Montana vote for statehood as a single state rather than multiple territories- they’re landlocked, so would become a vassal state to the surrounding countries (Canada, usa).

Next, tackle the US’ existing slavery and apartheid systems. The civil war is over, but slavery still exists in the form of Jim Crow laws and such.

The next hurdle to cross is the rampant corruption inherent in the system. This era already had a great deal of progress- antitrust legislation primarily. I shepherd these movements along and make them stronger.

At the end of my life, from 1900-1920, (I’m 36, going back to 1876, so I’d be 60-80) I make sure to eliminate the political figureheads that destabilized Europe throughout the early 1900s. It’s important to stabilize what is now the EU.

Just for curiosity sake, kill both Marie Antoinette and Louis XVI some time in their life long before coming into power.

I would need to know, though, whether, considering we are already bending the books rules by killing already dead people, I could get away with looking at a portrait/painting/whatever of a person and use it to kill their younger self.

Because otherwise, I would probably kill Napoleon just for fun. No other reason than to have the history books say he climbed into a loaded cannon and was shot out with the cannonball.

My own family ancestors. If I’m never born I can never die, and become a god!
Reference from “Rant, and oral biography”

Woodrow willson The leaders of the SPD in germany between 1919-1923 exept Stresemann Andrew Jackson Those are the names that come to mind right away

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Easy pick. There was this secretary to Aurelian who made some corrupt stuff and then knowing how Aurelian is against it forged his letters to make his guards kill him. Wonder what would happen to the Roman Empire if Aurelian ruled more than 5 years.

Wait 2 more years and kill Stalin or just kill Lenin.

I’m going back in time and killing both my parents so we can see what happens to me.

His whole bloodline. I’d do the research, and make sure I get his family tree.

I have a special and unique hatred for Diego de Landa, burner of the Mayan books. I would remove him and as many of his associates as possible from history.

Ooh, looks like Emperor Constantine was just smote by a thunderbolt from a clear blue sky in full view of the entire senate.

Maybe we won’t be spreading that cult he liked around, seems like it pissed off Jupiter something fierce.

I’m going back to the like 1780s and going full John Brown.

Adam and Eve

Benny Harvey

It can also work up to 150 years in the future, but you have to pay half your lifespan for the future eyes to really use it