Scarlet's backstory has her being abandoned by her father - apparently getting lost via a drunken bet - and somehow managing to claw her way to the top of the bandit cell that bought her. From there, she was able to successfully unite all of the different bandit clans of Armello under her rule as "The Bandit King" (more on that later), and kickstart a revolution to overthrow the maddened king with the assistance of one of said king's former knights, an expert thief, and a fisherman who may or may not be an eldritch cultist. She's also revealed to be the one that got the 4 Great Clans involved, manipulating events so that all four of the groups would engage in a civil war with each other as well; Scarlet's end goal is to take the throne for herself and apparently dissolve the clans to unite them under her banner.
Her whole characterization feels just a bit too... out-there, really. She's not entirely villainous - I think the writers were trying to go for a female version of Disney's Robin Hood with her, really - but her whole backstory is a bit much, being this ridiculously competent leader capable of manipulating everyone flawlessly. Her general personality being this smug prick that's always ahead of everyone, as well as this basically perfect leader of the Bandit Clan that's also able to easily recruit others to her side... it reeks of self-insert. All the rest of the cast of characters feel comparatively more grounded, but Scarlet just feels... out there. Seriously, what's with foxes always turning into Mary Sues?
I admit that I don't hate her, but... well, she's not my favorite.
As for the "Bandit King" bit I mentioned, it has to do with the aforementioned "queens tend to ruin the country" bit; the stigma of that means that most female powerplayers hesitate to refer to themselves as "queen", since they have so many negative connotations. Relatedly, the fact that Magna is openly calling herself the future queen - along with the country's most negative rulers all being female wolves - says... well, it says a lot.
Anyways, that's all I got on her; there's probably a few bits that I missed on her, as I haven't read the novella for her just yet, but what I've read so far isn't appealing.