Rank the DCEU villains against MCU villains

I really don't think he understands the relationships between Mercy and Lex and Dooku and Palpatine.  Palpatine was using Dooku.  Dooku was a tool to get to Anakin, the more powerful Force user.  Sith Lords use apprentices as tools.  Mercy is Lex's version of Harley Quinn (both created for the DCAU as the main villain's assistant).  He doesn't like her in the romantic way, but he'd hate for her to get hurt or die.  The way they used Mercy in the movie was sickening.  She's more than his assistant, she's his bodyguard.  Hell, if anything, she should have been in the Doomsday spot. She got to the point where her limbs can transform into weapons like Cyborg.

Well, actually, I would file Pierce under the "Corrupt, Conspiring Politician"-type of villain.

Oh, yes, The Vulture rocks. Keaton applies exactly the right levels of humanity and swarm.

Awesome! I'm sad Guardians 2 doesn't play around where I live anymore, else I might do the same thing.

You MCU fans are so dumb that you always need everything spoon fed to you. It doesn't matter if Mercy was loyal to Lex.

For Wonder Woman, it wasn't about deserve, it was about what she believed. And for Lex, it wasn't about loyalty, it was about expendability. Lex considers all of his employees, including Mercy, to be expendable.

No, Spider-Man's lack of Spider Sense is still the worst adaptaion because Lex not giving a damn about Mercy has been done in past media before.  Watch the episode Ghost in the Machine from Superman: The Animated Series.  That episode shows that Lex doesn't give a damn about Mercy so BvS took inspiration from that.

And that is where they (and you) don't understand the characters.  They changed things to the point they are In Name Only.  She might as well been Ms. Tessmacher.  But, then again, that would have been a big change, also.

What was the point of bringing up Wonder Woman?

Exactly this. As said before, Mercy could've been a real stand out character in the BvS and could've worked in multiple ways in future films - In the comics she is an Amazon, this would've been a good way to explain why Lex was keeping tabs on Diana because she told him about her, as well as other things like the Gods of mythology and the aliens out there in the known universe which would've added more dimension to Lex's scheming. Making her a cyborg, like in other media, would've been a good way to foreshadow Cyborg and Metallo. Or heck just having her be a kick-ass bodyguard would've been enough to make her a scene stealing character. In BvS she did little to nothing, you could've called her "Miss Ima Goodworkerlady" and it wouldn't have made a single difference.

Hell, they had an easy way of explaining why we didn't hear a peep from Batman during the Kryptonian attack and why Joker and Harley are still alive despite Batman being fine killing people:

Some time in the past, Joker and Harley kill Robin. Batman finds them in the middle of it and goes into a blind rage beating Joker to a pulp. Robin gives some sign he's not dead so Batman gets him out of there while the police collect the battered Joker and terrified Harley.

Robin dies, and Batman is broken up enough over this to retire. Joker is in a coma and has to have metal teeth and stuff installed to make up for the sheer damage Batman did to him this time, and Harley is sent to Prison.

Batman comes OUT of retirement after Superman debuts and the Kryptonians attack, but now he's more bitter and ruthless. This is why Clark is only noticing him NOW and didn't mention anything about him in MOS. Also he wonders if this is a new Batman copycat and not the older more noble one.

Joker remains in his coma at Arkham until someone plays a news report about Batman coming back, this wakes him up and he makes plans to escape and get Harley. Setting up Suicide Squad.

Lex is a thing to get to other things.  He's worse than an MCU villain in that he doesn't even need to be in the movie.  He's incidental to the movie.  What happens in the movie that has to do with Lex? He acquires Kryptonite so Batman could get it to fight Superman.  Batman could have gotten it from a museum or had it brought over himself.  Actually, that would have been a cool scene to have Bruce (instead of that faceless/nameless guy) walk onto the beach when the kid pulls it out of the water.  That makes the senator useless because she was only there to not get the Kryptonite into the country (so Lex had to smuggle it) and die in a pointless scene.  Even then if they took Lex out of the equation, and left the senator, Keefe could have brought the bomb in himself.  He was disgruntled with Superman, so there is his MO.  Then Lex is the one that gets Superman to fight Batman.  Lex is unneeded for this because they had reason to want to fight without him.  The last thing that Lex is there for is to create Doomsday.  Also unneeded for this.  The ship was still working.  The robots inside were still flying around and the overall computer systems were still running.  Have it that the scout ships go out and find dead Kryptonians (they are constantly scanning) and bring them back to the ship.*  Over the many months between MoS and BvS, Doomsday (Bizarro is a better idea for this) is created out of Zod's tainted (Phantom Zone) body.  This would be foreshadow for Justice League and why it takes so long for Kal El to come back.  The ship identifies Kal's dead body and bring him back to the ship.  Since his body isn't tainted by the Phantom Zone, he'd come back as himself.

*This would be a precaution for when scout ships and teams might land on a hostile planet. Also, Kryptonians recycle themselves anyway.