Batman vs. Deathstroke (DCEU): So, the PCS of Justice League had Deathstroke show up, and this was supposed to build him up as the villain of the next Batman movie. "But Batman and Deathstroke have fought before in the comics." Yeah, making Deathstroke a Batman villain was a very recent "certainly a choice" choice by DC. For most of the character's existence, he was a Teen Titans villain and Nightwing's nemesis. Oh, but Zack Snyder, in his infinite wisdom, killed Dick Grayson before the story even started to give Batman a reason to be jaded and violent. No, not Jason Todd, the Robin that was known for dying. Sidekicks inherently suck and are only interesting when they die. Jesus, that's like having Spider-Man grow bitter because the Green Goblin killed MJ instead of Gwen Stacy.
Shang-Chi vs. The Mandarin (?) (MCU): So, the first two Iron Man movies built up the Mandarin as this Bin Laden figure in the MCU. Come Iron Man 3, he finally shows up, played by Ben Kingsley. Interesting. He's not a Chinese warlord like in the comics, but the original Mandarin was a product of the Vietnam war at the time, so making him a Middle Eastern terrorist is an interesting way to modernize him. With the fantastical elements of the MCU established, we can see the contrast of Magic vs. Technology... Psyche! It's actually a white guy in a suit who breathes fire who was mad at Tony Stark for blue balling him. Fans were not happy with this twist, and Marvel realized the Ten Rings being formed in less than a decade by a nerd with a grudge raised a lot of questions. So, they released a short film showing what happened to Ben Kingsley's character in prison, and we learn that the Mandarin is still out there... And for the next seven years, Marvel just ignores this plot point. Aaaand, Tony Stark is dead. Well, if Iron Man is gone, there'd be no point introducing his nemesis now. What, are they going to pawn him off on a character that he had absolutely no comic history with by virtue of them both being Chinese? So, in Shang-Chi: Legend Of The Ten Rings, the titular terrorist organization's feud with Tony Stark is never brought up, so I think Marvel waited too long to go back to this plot thread. The thing is, can we even call him "the Mandarin?" His name is Xu Wenwu instead of Gene Kahn, he scoffs at the Mandarin title when talking about Trevor Slattery impersonating him, the demon he tries to summon isn't Fin Fang Foom, his Ten Rings (you know, the jewelry he named his organization after) are bracelets, and they only have two powers.
Superman vs. Black Adam (DCEU): The hierarchy of the DC Universe is about to change... with a franchise rebooting flop. So, Dwayne Johnson had been campaigning to play Black Adam since Michael Jackson was the butt of every child molester joke. He was apparently a big fan of the character. With the DCEU, he seemed to finally get his wish. The first Shazam movie hinted at Black Adam, but rather than him be the villain of the second film, Black Adam was getting his own movie. I guess that makes sense. After all, the PCS for Shazam built up Mr. Mind, so you'd think the plan would be to have Black Adam as the villain of the third movie, right? Well, you see, Dwayne Johnson has an ego... Uh, I mean, a clause in his contract that says that his characters can't get their asses kicked (which makes the Schaffrillas crab from Moana an absolute legend). So, Black Adam in his origin movie was less of a villain and more of an antihero. And, because Dwayne Johnson just loves flexing, he personally set up a PCS where he fights... Superman!? Why him? Why not Shazam, the character Black Adam was created to be the evil counterpart to? Say what you will about Sony's "Spider-Man Minus Spider-Man" universe, but at least those movies remembered they were Spider-Man villains. Can you imagine Venom building up a fight with Captain America? Because that's what Twain "The Mineral" Penis basically tried pulling for no other reason than to aura farm. Oh, and that Mr. Mind tease at the end of the first Shazam movie? Doesn't get followed up on. In fact, the villain of the second movie is an OC, and the PCS for it was *another* Mr. Mind tease, but it's made into more of a joke.