Warning! Spoilers ahead for Black Cat #4.
Spider-Man and Batman share a very similar weakness in their respective universes, and their enemies are aware of it as well: both the Webslinger and the Dark Knight have a soft spot for feline criminals. While Spider-Man has had on and off again relationships with the Black Cat, so, too, has Batman been romantically involved with Catwoman. Unfortunately, both of these women have darker and criminal tendencies which can be compromising for these heroes' moral codes. Worse still, these relationships can allow for the heroes' enemies to take advantage and gain an upper hand.
While Spider-Man hasn't been romantically involved with Felicia Hardy for a while in Marvel Comics, they still have a bond and relationship that's ongoing. On the other hand, Bruce Wayne and Selina Kyle are very much in a romantic relationship with one another in Tom King's current Batman/Catwoman run from DC Comics. In any case, both of their dynamics are very similar: the heroes chase their cat rogues, and it's more of a game than anything else. Once they're caught, oftentimes the rules go out the window, meaning Black Cat and Catwoman have been able to get away with a lot in past comics.
However, this shared lapse in moral judgment is something that has apparently become public knowledge over the years in both heroes' cases. In the recent Black Cat #4, from writer Jed MacKay and artist Nina Vakueva, two reformed villains talk about if Spider-Man would stop Black Cat from stealing art, and it's confirmed on the internet that Spider-Man goes easy on her. Likewise, Tom King and Clay Mann's Batman/Catwoman has seen the Joker taking advantage of the fact that Batman usually looks the other way when it comes to Selina. As a result, he's been creating a rift in their relationship, one with the potential to cause some very real problems for Gotham thanks to Batman bending his moral code for Catwoman.
The fact that both Spider-Man and Batman are willing to tolerate a personal moral leeway for Black Cat and Catwoman creates a weakness and vulnerability for them both. Not only do they become partially responsible when/if they look the other way when either villainess does something truly immoral, but these relationships can also present the risk of becoming leverage to be used against them should a villain decide to exploit this weakness, just like Joker is doing in Tom King's series.
While it helps that both Felicia and Selina's own moral codes have shifted more towards the side of the angels in recent years, it's still a weakness in both Spider-Man and Batman to be taken advantage of given the right opportunity for their respective enemies. In any case, it is rather interesting that this problematic flaw is shared by both Spider-Man and Batman. While the two of them couldn't be more different in their personalities, their situations with potentially compromising cat-like counterparts are very much alike in both Marvel and DC Comics.