Bleach is an action shonen series based on spirits and the afterlife, and many of this series' Hollows and Arrancar characters are actually highly symbolic of the futility of a Hollow's experience as a restless soul. Not even the king of Hueco Mundo, Barragan Luisenbarn, could find purpose or salvation -- but at least he was incredibly strong.
Barragan was dethroned as Hueco Mundo's ruler and joined the ten Espadas under Sosuke Aizen's command as the Segunda. Barragan was easily one of the most powerful Arrancars and had deathly abilities to match, prompting him to fancy himself as the master of death and time. He was almost right, but was ultimately, poetically wrong.
Barragan's Powers & Abilities as a God-King Arrancar
Each of the ten Espadas is labeled with an aspect of death, and these aspects often reflect the powers and personalities of the Espadas. Barragan's aspect of death is senescence -- the deterioration of living matter. Barragan believes that his aspect of death is the strongest and most all-encompassing, and he will gladly boast about this in battle, as he did with Captain Soi Fon and Hachigen Ushoda.
In his sealed state, Barragan can surround his entire body by an aura that accelerates time, rapidly rotting and aging anything that gets too close. Living matter decays and turns to bone, stone can crumble apart, and even advanced Kido spells fizzle away, since not even they can last forever. Barragan's death aura represents the inevitability of time, as all things must come to an end. He doesn't need his hierro (armor) skin or his sonido to protect himself, since his rapid-aging aura keeps him completely safe. Moreover, his sealed state's powers are just the start.
When Barragan releases his ax-shaped zanpakuto Arrogante, his powers are bolstered even further. His death aura becomes larger and more effective, and he can wither away a rooftop merely by walking on it. All spiritual energy rapidly ages and dissipates when it gets too close, and Barragan can project this death aura with his breath. His Respira technique allows him to attack from a distance, rotting the flesh from people's bones in seconds. He can also control how fast the Respira moves, so he can toy with his opponents if he so desires.
Barragan's abilities may seem foolproof, but they aren't. His body's outer layer is shielded from his own rapid-aging powers, but the interior is not, so if his guts are somehow exposed to his powers, he will rot away and cannot halt this process. In the end, Barragan is simply another creature who fears death, and not even he can master it or escape it. He got impressively close to succeeding, however.
How Barragan Tried (and Failed) to Master His Aspect of Death In Bleach
Barragan demonstrated his powers in one fight during Bleach when he went up against Captain Soi Fon and her Lieutenant, Marechiyo Omaeda, both of whom specialized in assassination. Soi Fon tried to engage Barragan in melee combat, but Barrgan's death aura kept slowing down Soi Fon's kicks, rendering them ineffective. Barragan's aura also aged and weakened Soi Fon's bones, meaning her bones started breaking just from performing basic melee attacks.
Barragan toyed with Soi Fon by swinging his zanpakuto around and then releasing it, demonstrating his amped-up power to intimidate his opponent and glorify himself. He released a Respira to see if Soi Fon could dodge it and the aura touched her arm, rotting it from the fingertips to the shoulder. On command, Marechiyo severed the arm to contain the damage.
Barragan's death aura was even strong enough to protect him from a direct blow from Soi Fon's cannon-like bankai, Jakuho Raikoben, dealing minimal damage. Barragan's abilities were tested further when Hachigen Ushoda of the Visoreds then appeared and tried to contain Barragan inside a hardened fortress of Kido spells. Barragan broke free despite taking another blow from Soi Fon's bankai, and he rotted Hachigen's hand. Hachigen took a gamble and teleported his hand inside Barragan's body, and just as hoped, the aura surrounding Hachigen's severed hand began to rot Barragan from within. Barragan was helpless in the face of his own powers and soon decayed into ashes. In the end, death itself always wins.