Killer Queen

Abilities
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.

Bomb Transmutation
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 a trigger located on its index fingers middle phalanx, imitating the action of pressing down 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. The charge is so powerful that it is capable of destroying a unit of Harvest, a Colony Stand capable of dividing itself upon taking damage, that greatly injured Shigechi.

Matching Kira's desire to keep his murderous life a secret, anyone detonated by Killer Queen is completely incinerated with their body, their clothes and any personal belongings they were carrying being completely vaporized at the atomic level, 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.

Air Bomb Transmutation
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.

Sheer Heart Attack
Sheer Heart Attack (シアーハートアタック Shiā Hāto Atakku) is Killer Queen's second type of bomb, featured primarily in the arc Sheer Heart Attack.

This treaded automatic bomb detaches from Killer Queen's left hand, so any Stand abilities activated upon it are reflected onto Kira's left hand. Because Sheer Heart Attack is attached to Kira's left hand, the primary bomb can still be used when Sheer Heart Attack is active.

It is completely autonomous and has a great range, so Kira can safely engage Sheer Heart Attack and move a great distance away while it carries out its duties. It seeks out whatever the warmest object in the vicinity is, even changing targets the second a warmer object appears; upon reaching its target, it automatically induces an explosion with power and blast size equivalent to the heat of the target. If Sheer Heart Attack's explosion was set off by a non-human source, it will continue to seek out targets until it explodes from a human. Like Killer Queen's first bomb, Sheer Heart Attack's explosions remove all physical evidence of the target.

The body of Sheer Heart Attack is nigh-indestructible, withstanding countless blows from Jotaro's Star Platinum, but can still be affected by non-damaging Stand powers and cracked if pulled apart at the mouth with tremendous force.

Its main drawback lies in its autonomous nature, which will sometimes prevent Sheer Heart Attack from prioritizing killing Kira's intended human target(s). Secondly, since it needs to explode from making contact with a human target to fully dissipate, should Sheer Heart Attack need to be deactivated while actively seeking a target, the user must physically return in the range of Sheer Heart Attack to deactivate and retrieve it. Furthermore, Sheer Heart Attack can continue to be active even after Kira's hand has been cut off, seen when he uses this to escape Josuke and company. Cutting off his hand even gives Sheer Heart Attack more power, as well as the ability to withstand even Echoes ACT 3's 3 Freeze.

Movesets
E - Barrage

R - Bomb Plant (Press R Again To Detonate)

T - Coin Toss

F - Impact Bomb

H - Sheer Heart Attack