It is a complicated subject, even more so if you want to try to broach subjects like "financial abuse" and "emotional abuse" as some might (both incredibly nebulous concepts though*).
"He said, she said" is pretty much the outcome demanded by the idea of fair law (you could go for the Islamic one where a woman's testimony is worth less than a man's I guess) -- Blackstone's formulation as it would generally be referred to of better to let 1000 guilty go free than punish a single innocent, and if it is going to be a criminal matter then even more so (lawyers hate assigning percentages even more than doctors hate to say how long someone has to live for much the same reasons but for criminal then beyond all reasonable doubt means 99%, civil then being preponderance of evidence which is more like 50%).
Malicious improper reporting is a problem as well. False positives even at rates of 5% makes things worthless when you might theoretically have hundreds of thousands of reported instances, even more so if merely the accusation can be life ruining (I am sure we have all seen the fun and games with various colleges/universities in the US and how they handle various claims here, especially if we do go back to the Blackstone thing).
Several reports over the years of people claiming such things, possibly as and when the police arrive turning on the waterworks, only to have it refuted by secret recordings (phones are good stuff and several people had recorded conversations or enthusiastic/more than cordial text conversations proving dates and times do not match, there was a fun one doing the rounds where a woman smacked her face into a lift not realising the lift had CCTV), or it being used to take people out of the picture for a while (seeing bad PR of having some woman's, possibly self, battered face on the front page saying the filth did nothing then turn up and man in cuffs is a thing several forces do) and just long enough to take the money and run.
If ever there was a justified reason to not stick it in crazy then this is that, though it can also be hard to tell and other things as well (several stories over the years of "oh no my hyper religious family, better lie").
Biology complicates things as well -- if doing the standard man-woman thing (though stats for lesbian relationships are truly alarming) then massive strength disparities (and general combat prowess) comes into play. To that end if the woman in that scenario starts the fight (despite what schools seem to go in for these days when it comes to fights then the one the throw the first punch without other extenuating circumstances is generally the arsehole under the law) and the man retaliates at anything like full force and proper combat skills then...
Equal rights and equal lefts, even if physics say no... things to ponder.
Psychology is also a fun one every which way you care to consider it. Abusive relationships as a general psycho pathology** and more isolated then the shame that goes for both sexes when the victim of it (women is well known but abused men when "men do not hit women" conflicts with "losing a fight to a weaker opponent is not good" makes for very unpleasant outcomes, also quite dangerous for the woman in that scenario as snapping is a very real outcome and where you might be able to eventually walk away from a hard punch after a little sit down with some unpleasant injuries the proverbial seeing red and full on rage you won't) makes this all the more tricky.
*framing also comes into this one. Controlling what someone else wears is considered as it in most places "no woman you are not going out dressed like that". What instead if you frame it as "you are free to go out dressed like that, I won't be here when you come back though" (do follow through if you issue such an ultimatum -- hollow words are not cool and won't lead to you being well considered as nobody respects weakness, might pity it but that is not the foundation for much), or indeed just leave and if they ask then state that as the reason. Same end result, though the latter is personal preference at that point. Can also be adapted for many other scenarios but still under the general remit. It also says nothing of some people like to push and test boundaries in relationships, though some call it shit tests, and have it as a way they roll.
**going to have to be the arsehole that posts a ted talk but it is quite enlightening and covers the general layout, warning signs and more.
To end on a more controversial note then black and white thinking can be hard in this as well. While I still firmly advocate for don't stick it in crazy then there are those that say don't throw away those for a mental illness (
https://www.who.int/news-room/fact-sheets/detail/mental-disorders says 1 in 8 worldwide,
https://mentalhealthfoundation.org/mental-health-statistics-2021/ for 2021 says 44.8% of US adults over 18 accessed mental health services in the last 12 months, females at 49.7% and that number set to get higher as time goes on***. It may also be one of those things rather under diagnosed, especially men but enough women also adopt "walk if off"/don't show my weakness lest I be kicked out of the pack these days. Depending upon your age then if you are looking to do the relationship thing your numbers may be even more skewed
http://web.archive.org/web/20180810...8/08/online-dating-out-of-your-league/567083/ .
https://www.huffingtonpost.co.uk/danny-baker/mental-health-and-relationships_b_5513500.html is an interesting take as well, though for me scenario 1 is also off the cards). To that end one and done is tricky if one (which could even be a destroyed wall rather than bruises) is a result of some kind of PTSD (military, law enforcement, medic, childhood, previous relationships/relationshits, twitter arguments****...) or similar concept, and that is not even considering the effects of the person doing the one if you then remove their family, kids, support structure, possibly employment and all the other things that keep people tethered to reality.
***in the US people seem to live isolated lives, possibly without children, without connection and probably extreme financial hardship both now and even more so. Some humans can handle it, will be interesting to see what goes in a few generations if that gets selected for by whatever means, most can't though as we are evolved to be tribal creatures.
****don't get me wrong I find it as hilarious as anybody to see people so fragile and weak despite no apparent reason to be but for the same reasons that even those faking illness have something that needs addressing if indeed it is a genuine diagnosis of it then so it goes.
