First of all, there is no one solution.
The eradication of tannin on a teapot
will call for a different methodology
than one you might apply to
blood on a blouse
coffee on carpet
shiraz on sheets.
If it sets you’re screwed.
Don’t scrub or soak
unless you know what you’re doing.
Consider a degree in Chemistry
or, if funds are no object
and the environment no matter,
replace the blouse, the carpet, and the sheets.
One way or another, all stains are delible.