What are the skills and knowledge you could actually bring & fully realize at some point in the past?
And we're taking this in the strictest, nerdiest, materialist lense. I don't care how smart you are you ain't making a steam engine the in bronze age, for instance.
So what could you create, with just your knowledge & period tools? What kind of institutional, technological, philosophical innovations could you realistically recreate? How would you interface with the social fabric of society to not be some crazed pariah who never positively influences the place they went?
Germ theory and using alcohol as a disinfectant. Even if you can't prove the science without microscopes or whatever, being able to make people not get infected wounds and die is both beneficial and doesn't require a huge baseline of technology.
soap & handwashing around open wounds, idk how well non distilled alch would work (if youre in some time before distilleries).
getting people to do it though... "powers" of healing often get mixed up in religion i wonder how to navigate that
If you were in a cold climate I imagine you could get somewhere with Freeze distillation where you just put your alcoholic whatever outside to freeze solid, then turn the container upside down over another container to melt slowly inside. The alcohols will be among the first things to melt.
You can do this several times but IIRC the best you can manage is about 45% or 90 proof. Hand sanitizer is only 60% alcohol so I imagine 45% would be fairly good for most applications.