Disclaimer: This has nothing to do with backgrounds from D&D 5e.
It happens a lot that the story you create for your character sometimes is not well aligned with what happens afterwards in-game. If you are a Lvl 1 Warrior you maybe can say you fought in the frontlines of a bloody war, and now are a retired mercenary.
Then you end-up losing to a bunch of rats the GM threw your way because the ceiling was too low and you forgot your matches.
What I want to know: is there a table/resource that has some indicator of what you may have accomplished when creating a character of a specific level?
That way I won't embarrass myself narrating when I defeated a lich in my Lvl3 Ranger backstory, just to be inmediately destroyed by two goblins and their pet wolf in my first encounter.
I don't mind D&D/Pathfinder responses, even when the power level may differ between the two, and even between versions. I'm more interested if the resource itself exists, or how to create one.
Best Answer
There is no guide like this
What you're asking for wouldn't begin to cover the options players may want for their characters.
However, there is an easy solution. Pathfinder creatures that are not directly related to Paizo's Golarion story are mostly listed in as srd content. Looking around your level, or slightly higher, you could find something that your character could realistically have done.
Second, remember that little gets done by one creature by itself. Writing in former allies can be a fun tool for your GM that allows you to round out your story, perhaps with a more epic encounter.
Not all characters have to have survived some harrowing experience
That's about it. You don't have to be an orphan. You don't have to have defeated a Lich (typically a CR 12 encounter), or survived a war. If you're level 1, you're barely better than an NPC. By level 3, you stand out in a crowd of adventurers. Practice writing more interesting things about a person who would want to engage in a war or slay a lich. Save the heroics for someone whose level justifies it.