Out of all of the "Twisted Disney" pictures you've done, this is my favorite. The main reason is that it feels more grounded than a lot of the others, with Marian's transformation being due to something very much possible within the film itself (Robin's death from being shot in the moat). A lot of the other pictures, though creative, sometimes felt like they were stretching to justify the Princesses becoming darker. By keeping this one more subdued with a simple revenge story (much like the Nala picture), this became the most believable of the bunch.
I also like the fact you put in Skippy at her side, as it gives an indication of a mentor-student relationship between them without saying it straight out. It makes sense, given how Skippy met Marian during happier times and similarly idolized Robin enough to help him in his fight. I also enjoy how Marian still has her traditional garb, only it's now torn from battle and to allow greater range of movement. Changing her hood from being a sign of her ladyship to a symbol of her scarring and outlaw ways is similarly pretty clever.
All in all, it's a great demonstration of how to do a dark "What If?" story.