If someone told you that you could have any anime ability, would you pick the coolest single power that you could think of? Or would you pick a power that is the anime equivalent of wishing for more wishes, the ability to take on other people's powers as your own? Though rare compared to fire wielders or ice warriors, anime characters with power absorption abilities are some of the toughest fighters out there.
Exactly how this ability works varies from person to person - it can be as absurdly complex as Chrollo Lucifer's multi-step Nen attack, or as simple as a plant Pokémon's Giga Drain. It can have serious side effects like memory loss, as it does for Yu Otosaka, or it can have seemingly no drawbacks, as in the case of All For One. Sometimes, anime characters who can steal power don't have the inborn ability to do so, but go out of their way to take from others, as is the case with Danzo Shimura.
This is one of the most versatile abilities in all of anime - but because it leaves its victims without their power or even without their life, it's also one of the most cruel.
As the sin of Greed, Ban has an incredible ability called Snatch. Snatch allows him to steal literally anything from another person, from money and weapons to magical abilities and even organs. The ability does have some drawbacks - for example, if he uses it on someone else with the ability to absorb another person's power, they'll be able to take his powers instead. Also, he can't steal more power than his body is physically capable of containing - trying could result in serious injury.
All For One - My Hero Academia
All For One is one of the most terrifying villains in the world of My Hero Academia. One of the reasons for this is that he's capable of taking other people's quirks (superpowers) and making them his own. He can also combine quirks that he's stolen into new abilities, as well as force onto other people. Like the man himself, this ability is called All For One.
Yu Otosaka - Charlotte
Though he doesn't discover the full extent of his abilities until the end of Charlotte, Yu Otosaka can use a technique called Plunder, which allows him to extract other people's superpowers from their bodies and use them himself. While this means that he possesses hundreds of unique abilities, it does come with a downside. If an ability comes with any negative side effects, he absorbs those along with the positive - this can involve nausea, temporary blindness, or worse. Even more extreme, acquiring these abilities comes at the cost of his memories - his brain simply cannot retain all that information at once, so it gets rid of "extraneous" details, including important life events and relationships.
Chrollo Lucifer - Hunter X Hunter
Chrollo Lucifer's Nen ability, Skill Hunter, is one of the more complex ones on this list. He can steal another person's Nen ability, but only if he fulfils a few tricky requirements. First, he conjures up a book called Bandit's Secret, and turns to the page that describes the ability he wishes to steal. He must keep the book open to that page while he battles, which limits his range of motion. Next, he has to see his opponent use their ability, ask them about the ability and receive a verbal reply, and get his opponent to place their palm to the handprint on the cover of Bandit's Secret. All of that has to be done within an hour or it won't work. With an ability that strict, it's amazing that Chrollo is ever able to activate it - but because he's such a talented fighter, he makes it work.