2017 saw the arrival of a fully formed, heroic, flawed, realistic, human, ambitious, directed and articulate female character the likes of which audiences have supposedly been begging Hollywood for for years.

No, I'm not talking about Wonder Woman. Compared to the character of Elizabeth Sloane, Diana Prince is just another costumed superhero in the same kind of movie as all the other superhero blockbusters, she just happens to be female (not too far from the truth even when not comparing Wonder Woman to other female-centric movies, as absolutely nobody seems prepared to admit).

It's not about the crisis moment when her choices bring her undone, and it's also not about the twist of the last scene that reveals Sloane was – as she continually exhorts of herself and her profession – three steps ahead of everyone.

She just has every facet of a real woman the likes of which we've been told we've long deserved. She's whip-smart, usually the smartest one in the room. She's got very human tastes and desires, engaging a male escort service to satisfy her sexual cravings like it's just another biological function she knows she can't ignore, moving on decisively afterwards like she's just drank a glass of water because she's thirsty or visited the restroom because she needs to empty her bladder.

Sloane also has ruthless ambition to go with her smarts. She can argue anyone around her under the table. She's a natural leader, either inspiring through example or forcing through fear of her withering wit. She knows what she has to do and lays out a plan that's so expansive it's not revealed even to us until the final frames.

But Elizabeth is no superhero. She runs on adrenaline and the thrill of winning as much as the bottle of pills (whether they make her sleep or keep her awake is never established, but it's just as obvious to Elizabeth herself as it is to us that she's living on borrowed time to make her mark).

She's a Washington lobbyist, and when we meet her she's facing a congressional hearing to decide whether they're going to convict her of financial irregularities and send her to jail. The script by newcomer Jonathan Perera has been described as Aaron Sorkin-like, but that's not the half of it.

By virtue of its existence, every movie or TV show lifting the curtain to show how American politics works behind the scenes must be smarter and further obfuscate the real machinations of political power and its corruption than the last movie, and when we meet Miss Sloane she's been navigating the extremely muddy and pliable waters of buying off congresspeople in order to have them vote in the interests of her corproate clients with aplomb.

The latest mark to approach her firm and seek her services is gun manufacturers, hoping to whip up public support to overturn a restrictive bill by generating interest in buying guns among the female demographic.

In a move that's partly shocking and partly suits her to a T, she turns on a dime and decides to accept an offer from a competing firm opposing the powerful gun interests. Some of her colleagues wonder if it's because of gun violence in her past, but in throwing away a position at a top tier firm, it's simply because Sloane thinks she can spin the issue and win against the odds – winning is her most driving motivation.

She proceeds to cut a swathe through the debate to the astonishment of her collegaues (many of whom she's poached from her old firm) and her new boss, firm owner Rodolfo (Mark Strong). But even when the story reaches that most Hollywood of plot turns – when she realises that winning might come at too high a price – Sloane is completely in charge of what she's doing.

We don't always like her and we're not meant to, but it's such a fantastic characterisation and it's so refreshing to see a woman in a film who doesn't apologise for who she is and what she wants, who isn't co-opted neatly into the Madonna/whore dichotomy where we can be assured she's no longer a threat. Sloane is a feminist who's only in it for herself, exploding through glass ceilings with victory rather than sisterhood in her sights. We even get a very satisfying denouement to what was shaping up to be a slut-shaming moment during the climax, further galvanising how gender-aware the script is.

The plot can be summed up blithely as simply being about a smart female lobbyist doing what lobbyists do, with the sparky dialogue and a good deal more than the drama than we expect. Chastain is the eye of the hurricane here, as commanding as she is physically slight and as pretty as she is ballsy and abrasive. I gather from evidence online that most people thought she played a great character but that the film around her was a weaker effort and it's a shame, because while we're all (apparently) howling for great women characters, ones like Miss Sloane had been under our noses the whole time.

Chastain has been a very outspoken proponent of better roles for actresses, and she's certainly put her money where her mouth is here. Even if you don't get much out of the rest of the film, this is one of those performances where in years to come we'll be saying we'd watch her read the phone book.