Butcher I had increased strength and durability, a ranged agony-infliction aura potent enough to induce cardiac arrest, and the ability to transfer a watered-down version of his powers and a share of his consciousness to his killer, making them the next Butcher.
Had any Butcher been killed by the Simurgh, the Simurgh would not inherit their minds. Butcher's powers would likely go to the nearest available parahuman - given the Simurgh, probably someone inconvenient.
If Butcher get multiple copies of the same power, they will stack. 
A succession of fourteen different parahumans have added their own abilities and minds to Butcher. In addition to granting more powers, the Butchers' minds will drive successor insane if s/he isn't a member of the Teeth who challenged the previous Butcher and beat him in a fair match. For example, Butcher III was driven mad for being a hero.
Butcher XV is likely to have access to the following powers:
The ability to cause excruciating pain at range and increased durability (I).
Superhuman strength (I, III, VI, IX, XI, XIII).
The ability to see hearts, veins and arteries even through walls (II).
Short-range danger sense against physical attacks (III).
Her attacks bend space to create perfect accuracy, never missing a target within range.
A tall, elegant, woman, with a long neck and long limbs. Her costume has an Asian feel to it, and is trimmed with razor-sharp blades. Her costume is also busy, displaying elements of samurai, headhunter, and bloodletter, but not necessarily elements that portray her as "Butcher." Among her weapons is a massive bow, requiring her inherited super-strength to draw. Killed herself because of the suicidal despair created by Cherish in a fight against the Undersiders.
Current Butcher. After Cherish became the new Butcher, Tattletale hired workers to move Cherish's pod from the waters near Brockton Bay to a more remote location. Tattletale speculates that Butcher 15 will only get a chance to kill fish, and joked that maybe Leviathan will pass by and kill himself.
There is speculation that the original Butcher's powers came from Cauldron, given that one of the vials' powers mentioned to have been tested included "a power that allows one to take over a nearby parahuman’s mind, body and powers automatically on death". However, given that even in a hypothetical world without the existence of Cauldron there still exists a "Butcher Queen", this theory might not be entirely correct, if the "Butcher Queen" is meant to be an alternate version of the Butcher.
The ability to transfer a share of consciousness to killer can possibly be classified as Transfiguration Brute.
↑Lunatic Blue I have a question, what does the Butcher mean for shards/entities? Is it an aberration?
Wildbow keep in mind that the shards are pieces of the entities, they have residual effects & processes from being part of a larger organism, so where stuff isn't skewed intentionally, sometimes you just get quirks running through. - Wildbow on Discord, archived on Spacebattles
↑ 2.02.12.22.3“The first Butcher had super strength, durability, and the ability to inflict enough pain at a distance that his enemies went into cardiac arrest. His other powers only became evident later. He was killed by a subordinate, and the man who would later be known as Butcher Two inherited a fraction of his powers and a share of his consciousness.”
“Butcher Three inherited it too, along with a share of Two’s powers and consciousness,” Tattletale said. “He was a hero, though.”
Accord rankled at the fact that she’d spoken out of turn. Her voice rang in his ears, as though each syllable were the echoing toll of a bell, growing louder with each iteration. Out of turn, out of sync, out of place.
He bit his tongue. “Yes. And the two voices in the hero’s head worked together to drive him mad. He was gone from this world well before he died in battle. The Teeth reclaimed the power, and the legacy has largely remained within the group since, each successor inherting powers of the ones before. The voices and consciousnesses only work with rightful heirs, members of their group who challenge the leader and beat him in a fair match.”
“Which one is this?” Regent asked.
“Fourteen,” Tattletale said.
“This one’s number fourteen?” Regent asked. “Which means she’s got thirteen sets of powers?”
Another one, speaking out of turn, Accord thought.
Citrine was giving him a sidelong glance. He met her eyes, shook his head fractionally.
Tattletale answered, “Only a small share of each power. Don’t forget she’s got thirteen voices in her head, giving her advice and helping her work stuff out, and all the powers she brought to the table, besides. Her attacks don’t miss. She imbues them with an effect which means they bend space so they strike her target, Bullets turn in midair, swords curve, all means she’s pretty much guaranteed to hit you if her attack reaches far enough.” - Exerpt from 20.y (Interlude; Accord)
↑dvdjspr I'm more interested in what exactly would happen if Ziz killed Butcher. Would she still inherit their minds? Would a Simurgh with 15 human minds be more dangerous, or less?
Wildbow The Simurgh would not inherit their minds. Butcher's powers would likely go to the nearest available parahuman. Given the Simurgh, probably the most inconvenient parahuman. - Wildbow on Reddit
↑razorsmile Butcher is scary. If she gets multiple copies of the same power (say, if more than one of her predecessors had superstrength), does it stack?
Wildbow There are no copies of the same power, barring a circumstance where it’s powers recurring within a second/third generation cape. Even then, debatable.
↑ 6.06.16.26.18.104.22.168.76.86.9Butcher didn’t react as bugs bit and stung, and capsaicin-laden bugs found her eyes and nose. Her skin was too tough, and she didn’t feel pain, thanks to Butcher twelve’s powers. She was composed as she lifted a gun that would normally have been mounted on the back of a truck. Without putting it down, she held it with one hand and donned her mask.
She turned our way, as though it wasn’t even a question. A sensory power.
Butcher two, the ability to see people’s veins, arteries and hearts through walls.
She teleported past the worst of Vex’s forcefield barrier. Flame billowed around her in a muted explosion as she appeared.
Butcher six’s explosive teleporting. It’s weaker than it was when six had it, shorter range, and the intensity of the explosion isn’t nearly what it once was.
Wounded but intact, the dog turned and snapped at her.
She was gone a heartbeat before the teeth snapped together.
Butcher three’s danger sense. Didn’t do him much good. Driven mad, died in a suicidal attack against the Teeth. Window of opportunity is lower, application limited to more physical danger.
She reappeared in a cloud of rolling flame, reversed her grip on her gatling gun and swung it like a club, knocking Bentley clean off his feet.
Super strength, courtesy of one, three, six, nine, eleven and thirteen. Cumulative effects. A little bit of super strength from multiple sources added up.
Bentley had recovered and charged her. She responded by hitting him with a wave of pain, putting him off his guard so she could strike him aside.
Butcher one. Inflicted agony at range.
Butcher had a grip on Regent, threw him into Biter with enough strength to take the two of them out of the fight.
Possibly enough strength to kill one, if Lizardtail’s power wasn’t able to outpace the internal damage done.
Induces mindless rage. Power from Butcher Nine. Very low range.
Inflicts wounds that fester. Power from Butcher Four. Less effect than Four had. Far shorter duration.
Butcher had time to string her bow before she had to teleport out of the way, appearing on top of a building with a vantage point of the battlefield. She knelt, touching the rooftop, and reformed the stone into arrows.
That power was Butcher Eight’s, except he’d had more reach, was faster.
Butcher drew her bow again.
She didn’t miss. She did something to warp space or adjust the very fabric of reality, so her shots always struck the intended target. - Exerpt from Imago 21.6
↑“Not so risky when you’ve done a read on the situation. I had all the notes on Butcher Fourteen. She couldn’t teleport free, not into open water. She still can’t, and I had a crew use a remote control device to lash a cable to Butcher Fifteen’s pod. They’ve dropped her into a deeper area of the ocean, and the only thing she’ll be likely to kill are fish. If we’re lucky, maybe Leviathan will float that way and off himself.” - Exerpt from Imago 21.y (Interlude, Parian)
↑Cherish – An amoral emotion detector and emotion manipulator who uses her powers to find targets for her group, the Slaughterhouse Nine. Twenty, she sports a stripe of violet in her dark hair. - Cast (spoiler free)
↑ 9.09.1Less than a year ago, Butcher had been known as Quarrel, and as Tattletale told it, Quarrel had used a much smaller version of that same bow to kill Butcher Thirteen in a drawn-out fight in New York. - Exerpt from Imago 21.6
↑“The powers are poor,” the Doctor said. “Foreign, yes, but poor. When we tested these, we got a defensive power utilizing warped space and a power that allows one to take over a nearby parahuman’s mind, body and powers automatically on death. The one I hold should have attack or mover capabilities, if not both.” - Exerpt from Venom 29.7
↑Assuming that Cauldron's operatives maybe killed Eden but then just sat on their hands/died, the Endbringers don't exist, the cauldron vials aren't spread out, and there's less of the really powerful parahumans here and there who're capable of acting decisively.
A coalition of villains occupy Brockton Bay, including Marquis, the Butcher Queen and the Little Doctor, while outside parties want a piece of that pie. - Wildbow on Spacebattles
↑Transfiguration brutes offer transformation and revival abilities. They arise from situations where death is sought or held at bay. - BRUTE, document by Wildbow