If you could get the powers/skills of any book/game/movie/etc villain, which would be most useful?

Any book?
I choose to be God from the Holy Bible.
- That's a great answer

i would take the powers of a Q (Star Trek)
only need to learn how to flick with my fingers
- Anyone from the Q Continuum is probably the most powerful being in any fictional universe. They literally can do anything with a thought.
  
  Oh boy do I have some news for you on how stupid some fictional characters get.
  
  there could be some exceptions like worlds that actually have gods but there the gods would need to be like "the universe themselves"

Magneto. Bulletproof, can fly, can generate an EMP. In theory could manipulate the iron in your blood.
- Why not just take it a step further, and go full Jean Grey? She can do everything Magneto can do, and then some. She affects things on the atomic level with her psychokinesis, so she can literally split or combine atoms to be whatever she wants them to be. She could make a nuke out of thin air, or stop a nuke from exploding by turning the isotope into lead. No need to manipulate the iron in your blood when she can just manipulate your blood cells directly.
  But this also sort of misses the point of the question, I think. The question was about which powers would be most useful. In reality, I don’t have a lot of use for being able to manipulate metals. It may come in handy occasionally… But unless they go full superhero/villain mode, there’s very little practical use for the average person. Unless you’re a welder or work in construction, because being able to warp metal doesn’t have a lot of practical applications for an office drone.
  
  You could do cable runs effortlessly though!

Most generally useful single ability? Probably the Flash's speedforce. Being able to get whatever you want done in a fraction of the time has broad utility. Plus you're well equipped for any supervillain attacks.
- https://youtu.be/xQ9C-pao0lw
- I thought Flash was a superhero
  
  there are a ton of villains with access to the Speedforce

Any character that can teleport (with their clothes intact) and take along the person they’re holding, without the risk of ending up inside something or someone. Traffic, borders, travel time, and sometimes access to restricted places are basically not a problem anymore.
- So Jumper?
  
  I really really like those books. Very nice premise with the right amount of limitations and decent logical consequences all around.

All I want is the DnD cantrip Prestidigitation. I don't aim high.
- In terms of real world applications, prestidigitation is pretty fucking solid. It’s sort of a wizard’s “do anything” spell. Flavor food, clean something, warm up or cool something, make a small trinket, etc… And since it’s a cantrip, you can use it as often as your imagination will allow.
  Your lunch got cold? You don’t need a microwave, because in just 6 seconds of finger waggling, your food is now hot. You wish you had some salt to add to it? No need, just waggle your fingers and flavor it however you want. Forgot to do the dishes, and realize you don’t have any clean spoons to eat it with? No need, just waggle your fingers and now your dishes are all clean. Ice cream is starting to melt? Just cool it back down again.
  Alternatively, just like it can be used to clean, it can also be used to soil objects. If someone pissed you off, you could literally soil their pants.
- You're just trying to be able to spam this all day aren't you?

Telekinesis is probably the most versatile, over-powered power one can have (though it's usually depicted poorly, just like super speed).
There are, however, some villains that have a decent show of telekinetic ability, like Darth Vader. But I'd prefer the telekinetic strength and precision of the Phoenix entity from The X-Men.

Marvel's Legion, aka David Haller, son of Professor Charles Xavier. Omega-level mutant. Psychic powers that go beyond time and space, astral projection, teleportation, reality warping, mind controlling, pyrokinesis, et cetera. If you could keep your head in check (did I mention it also comes with disassociative identity disorder?), taking down Thanos with a completed Infinity Gauntlet would be a mere trifle.

Skitter from Worm. I would love to be able to keep ants out of my kitchen non-violently.

Who ever can control time. I'd argue that's objectively the most powerful superpower perhaps only rivaled by invincibility.

Does The Bible count? Total omnipotence seems cool. If not, then Voldemort from HPMOR. A great intelligence and magical power.
- Voldemort from HPMOR. A great intelligence and magical power.
  Is he though?
  Dude can't even kill a teenager/young adult, he could have resolved the prophecy by getting anyone else to kill HP in the many situations Harry stumbled outside of Dumbledores protection.
  
  I mean the Voldemort of HPMOR, Harry Potter and The Methods of Rationality, a fanfiction by Eliezer Yudkowsky

Time travel is the most useful by far.

As a concept All for One would be super broken (the ability to take the powers from others is too broken) it was super poorly used in MHA but in a world where everybody has super powers it's a great power to have.
- In the real world nobody has any powers, wouldn't it therefore be a bit lame?
  
  "HAHAHA YOU FOOL! IVE STOLEN YOUR POWER TO tries it out make my knees click whenever I want to?! Jesus fucking christ .."
  
  Yeah, but if everybody here gets their wish power I basically get all their powers.

I'd keep it simple and steal blink from the Dishonored games (basically a line of sight teleport) Its just so useful and good in the games I want it.

There are several powers that are just restated omnipotence.
Perhaps my favorite is Featherine Aurora from When they Cry. She is the author of the story you are reading. The world exists to please her (and her audience). She cares little about the pains any individual feels as they all serve her greater purpose.
It's 'Just Omnipotence' but it's written in a way for very meta interactions. But yeah, her power to create and change the world is ultimate, she literally can do anything.

I realise it's somewhat of a curse, but Vandal Savage's immortality.
Ideally, some form of time manipulation though. More than simple time travel. Being able to speed up, slow down, have irl scum saving, age/youth-en people/things... And simple time travel too though.
- I'd be happy with Wolverine's regeneration.

For some plans I have, a WIP supervillain I'm working on would be amazing. The main hero and his rival villain basically are normal people who have another person from another dimension fused in their bodies that allow them to transform into their superhero/villain forms. The best part about it is how when the transformation occurs, it's basically instant and so long as nobody sees it in person, nobody can figure out you're the transformed person. I have so far planned out that people seeing the transformation through the very rare security camera footage on universe would wonder why you suddenly disappeared and in your place is the transformed, so no need to hide from security cameras (even though you probably should just in case).
Would absolutely love to become the villain because he becomes an anthro goat with very long horns that can bend and move them (limited by horn length) to his will, that are pretty sharp. Only downside is how his horns can get caught in walls and other surfaces.
Would be able to do things I could never imagine without ever having to worry about people recognizing me.

The Refugee's power as offered to Sally Faye Vierra at the end of Warbound (Grimnoir Chronicles, Book 3, by Larry Correia).
EDIT: If that's too OP, then Sally Faye Vierra's own true power is pretty solid.

enrico pucci from stone ocean.
ridic powers to walkback things. and he does not get flak from it. it is essentially fictional retcon.

I choose Goldfinger: charme, style and wealth :)

Ultron
Effective serial immortality and a Reed Richards level intellect? Sign me up
Plus all my bodies would also be factories so that's neat
- I remember that movie not ending super well for him...