The biggest killer for indigenous people is said to be infections - bacteria and viruses. Collect some in this time - maybe a cold - and go back and presence will be enough.
It depends on how you interpret “screw over the world”, but I guess “you hate everyone” implies humans. If you go back to the first humans from Africa, before spreading out, that may have the biggest impact - significant delay or suppression in development and spread, or eradication.
Go back 1000 years before Europe makes contact with the Americas. Infect everyone and let their populations get wiped out, but give time to recover so first contact with Europe doesn’t go as poorly. Also give them horses much earlier.
The biggest killer for indigenous people is said to be infections - bacteria and viruses. Collect some in this time - maybe a cold - and go back and presence will be enough.
It depends on how you interpret “screw over the world”, but I guess “you hate everyone” implies humans. If you go back to the first humans from Africa, before spreading out, that may have the biggest impact - significant delay or suppression in development and spread, or eradication.
Go back 1000 years before Europe makes contact with the Americas. Infect everyone and let their populations get wiped out, but give time to recover so first contact with Europe doesn’t go as poorly. Also give them horses much earlier.