Killer Queen is a visibly muscular humanoid Stand about as tall as Kira himself, light in color overall. It is portrayed as light pink in most media.
Its crown is flat, while two sharp, triangular shapes resembling cat ears stand on both sides of the top of its head. Its eyes comprise cat-like vertical pupils in front of its generally light-colored sclera. It has no nose, and its thin-lipped mouth is perpetually closed. It wears dark, studded, leather-like forearm-length gloves, mirrored in style by a garter belt-like band at its waist and ankle-height footwear. Its thumbs are additionally bandaged in white. Four short spikes line the top of its back. Its shoulders, the back of its hands, belt buckle, a plate hanging in front of its crotch, both sides of its ankles and the top of its feet all bear the emblem of a skull with ears resembling its own, in varying sizes and external decoration. In the anime, after receiving the third bomb, Killer Queen's eyes adopt a deep glow.
Later, the space behind its stomach is revealed to be hollow and suitable for storing an object.
The series is known for alternating colors between media, the information presented below may or may not be canon.
(White sclera and pink pupils)
(Navy blue gloves, footwear and belt, gray studs and golden orange plates)
(White sclera and light brown pupils)
(Deep purple gloves, footwear and belt, golden studs and plates)
(Punch sclera and white pupils)
(Deep purple gloves, footwear and belt, silver studs and golden plates)
Killer Queen is unusual among humanoid Stands with complete faces in that its facial expression almost never reflects that of its user, and is instead nearly permanently locked in a wide-eyed, neutral position. Exceptions to its otherwise stoic demeanor include it scowling at Jotaro as Kira realizes he had survived Sheer Heart Attack's explosion, and freezing in terror, mouth agape, as it is torn apart by the hands of Ghost Girl's Alley. Kira is able to speak through Killer Queen, as he does to Rohan while using Bites the Dust.
Killer Queen is a short-range humanoid Stand of average to above-average speed and melee attacking power. Although it is undeniably physically powerful, it is overshadowed by other close-range Stands like Crazy Diamond and Star Platinum, and thus Kira relies more on evading his enemies or using Killer Queen's set of powers to prevail.
Killer Queen's powers revolve around setting up different kinds of bombs that can annihilate Kira's enemies in one blast, making it a very dangerous Stand to face. Not only are the bombs powerful, but Kira is also able to deploy two initially, then eventually three kinds of bombs with different strengths, giving the serial-killer a large array of options when dealing with his foes.
Killer Queen detonates a coin.
Killer Queen may charge any object, inanimate or not, as a bomb simply by touching it.
Once a target has touched the object, Killer Queen can detonate the target by pressing its right thumb onto its index finger's middle phalanx, as if pressing a trigger on a handheld detonator; the charge immediately travels through the target's body before exploding. Additionally, Killer Queen can blow up the charged target itself, as demonstrated with Stray Cat's air bullets during the final battle with Josuke Higashikata; however, if someone else touches the charged target before Kira can detonate it, they will automatically be blown up instead, consuming the charge. This can also be done through direct contact with Killer Queen or Kira himself, skipping the charging process.
Matching Kira's desire to keep his murderous life a secret, anyone detonated by Killer Queen incinerates everything about them, including their body, their clothes, and any personal belongings they were carrying, leaving no trace; however, it is possible for a victim to survive an explosion if it comes from a nearby object instead of their own body, though this is a rare occurrence. Kira can also control the size and strength of Killer Queen's explosions as well as what parts of a victim's body are vaporized, usually resulting in Kira destroying his victim's body except for their right hand to keep. The effects of Kira's explosions on their surroundings vary; they generally do not damage nearby walls and floors, but during Kira's battle with Josuke, they could potentially affect nearby objects and Kira himself, though this may be due to Stray Cat's own Stand power being combined with Kira's.
There are several limitations to this ability. First, if Kira or Killer Queen cannot press their thumb against their index finger's middle phalanx to trigger the bomb's detonation, the target cannot blow up. In addition, since this power is similar to incendiary bombs, it also cannot induce their explosions if there is no air, as demonstrated by Stray Cat disabling a bomb by creating a vacuum around it. Finally, Killer Queen can only charge one object at a time.
It is unknown if non-Stand users can see or feel the explosions, but they can see a victim of an explosion die. Additionally, the explosion does not seem to generate much sound to anyone other than the victim, as Josuke and Okuyasu heard Shigechi call out to Josuke just outside of their classroom, but neither of them were aware of the ensuing explosion. Additionally, there were at least two other students in the same hallway as Shigechi when he was killed, but neither seemed to be aware of his demise as their backs were turned to him when he was killed and all evidence of an explosion dissipated within less than a few seconds.
During the final battle, Kira places Stray Cat (ストレイ・キャット,Sutorei Kyatto) in Killer Queen's hollow abdomen. With Killer Queen's Primary Bomb charging Stray Cat's condensed air bubbles, Kira may create virtually invisible air bombs (空気弾,Kūki-dan) to use as projectiles. These can be detonated automatically through contact or manually through Killer Queen's switch. Although he also cannot see these bombs, Kira is skilled in determining their trajectory using basic mathematical skills; additionally, Yoshihiro Kira can verbally help him direct his aim by flitting about the battlefield in his photograph form.
This Stand's abilities appear to draw inspiration from lyrics to the song Killer Queen – "She's a killer queen / Gunpowder, gelatine / Dynamite with a laser beam / Guaranteed to blow your mind / Anytime". Additionally, its appearance and eventual use of Stray Cat may be another lyrical reference, specifically. – "Playful as a pussy cat".
Araki includes Killer Queen's whole design among his favorite things to draw.
From the Stands up to Part 5, he considers Killer Queen his 2nd favorite in terms of design, below Gold Experience and above Echoes. The stand was designed to incorporate both the darkness surrounding Kira and the sort of eeriness a cat possesses.
At the 2019 Lucca Comics festival, Araki said that Killer Queen was his favorite Stand design-wise. 
↑Harvest - Vol.17 "Shueisha Jump Remix Stardust Crusaders Edition" P190 The origin of STANDS! Part.6