Katsuki notes early on that it doesn't matter to him that Tenya, Shoto, and Momo are rich, as he has other criteria for judging people. Later we learn why... It turns out Izuku is technically from a rich family due to his grandfather owning a robotics corporation.
With how powerful Regeneration is, why did All For One never consider taking it for himself, even after his first battle with All Might? We know he's careful about what Quirks he keeps for himself, so the most likely explanation is that it'd be redundant. With how many different Quirks he has, including several healing Quirks, he probably has enough to mimic Regeneration, meaning it would be pointless to try.
Stain's entire motivation is that he sees heroes other than All Might as parasites who only care about money or fame. Thing is, most of the heroes we see in Japan often have altruistic means for doing so (such as Uraraka wanting to help her family thrive). Now if Stain had tried his hand in America (say, with The Boys) he might have become a more respected vigilante instead of a wanted criminal. After all, many of the "heroes" sponsored by Vought are the exact sort of fake heroes he despises.
One of the Quirks loaded onto Midoriya's Zero Driver is the Search Quirk, which is also a Quirk used by Ragdoll of the Wild Wild Pussycats. However, while all the Quirks on the Zero Driver were stolen from All For One, it's been stated that this was done well before the training camp arc. Which means there might be a good reason why All For One wanted Ragdoll's Quirk specifically, with the rest of the Wild Wild Pussycats simply being a means of supplementing his collection.
Foxfire, Vector, Jackie, and Gear Woman are all Ms. Fanservice and have boyfriends (Infinite for Foxfire, Operatic for Vector, Cockatrice for Jackie, and Twice for Gear Woman). Bad Humor is only The Cutie and is single (her relationship with Yule Man is purely platonic). Maybe Choroi's just not villainous enough to pull off the sex appeal?
Graffiti can exist normally even as stencil art thanks to his Quirk, but anyone else will eventually die due to lack of oxygen. So why did Magne seem fine when she and Graffiti used Chalk Walk to hide from police after the two-year time skip? They can't have been searching very long, so most likely Magne just held her breath and waited.
On the one hand, it seems strange that people would buy that Trumpet is the leader of the Meta Liberation Army rather than Re-Destro, even with Jackie's power helping. On the other hand, what's more likely to be the leader of a revolution... A CEO, or a political leader?
We see in the first My Hero SCP One-Shot that Jalil (aka Crimson Death) knows how to help others avoid being possessed by an Akuma. This is more than just common knowledge. Jalil himself once got Akumatized (into Pharaoh) and canon shows that Mr. Ramier isn't the only one to get Akumatized multiple times. With how stressful working at a museum can be at the best of times (and Jalil worked at the Louvre before becoming a true supervillain) he's likely come up with a variety of calming techniques to avoid being Akumatized again and possibly wrecking his workplace.
It seems a bit odd that Yoshikage's villain code name is spelled as Ableblade instead of the more obvious Abelblade to fit the theme naming, but that might be the point. Remember, he was expelled from UA by Aizawa for wanting to ride on his brother Mechacain's coattails. The exact spelling might be part of his way of subtly trying to move away from that, and instead sending a different message across (that being he's an able combatant).
While Odion fits the Theme Naming of the previous incarnations of Odio, the pronunciation is off. With all the others it doesn't take much mental gymnastics to get the pronunciation (Odo can be sounded out O-Dee-O, the Wan in Ou Di Wan Lee translates to king, which in Japanese is Oh, hence Ou Di Oh Lee, OD-10 can either be pronounced one-zero or I-O). But when one reads the word Odion, they naturally pronounce it as Oh-dee-on. This actually makes sense when you consider Oersted's name also fits the Odio name, yet can't be pronounced as such by any stretch of the imagination, showing Oersted had the potential to not turn into the Lord of Dark, just as Odion avoided that same fate.
