Under the given conditions, Sosuke Aizen could defeat Zaraki Kenpachi in battle.

I'd like to begin by thanking Hopeliveson for taking this debate. Let's have some fun. As definitions and rules have already been taken care of, let's move right on to the arguments. ARG1: Numbers If one looks at Aizen's [1] and Zaraki's [2] stats under the "powers and abilities" section, they will find Aizen's stats to dwarf Zaraki's: 560 vs 390. Aizen surpasses Zaraki in all fields but Offense and Physical Strength, and even then, Aizen ties in Offense. Furthermore, while Aizen's Hogyoku allows him to boost his abilities even further [1], Zaraki's lack of Bankai [2] means his abilities cannot be increased. In summary, Aizen's statistical superiority to Zaraki and ability to increase that superiority indicate that Aizen would best Zaraki in combat. ARG2: Speed Aizen's significantly greater speed grants him an edge over Zaraki. Zaraki's speed - even without the limiting eyepatch - was barely, if at all, greater than that of Ichigo Kurosaki in mere Shikai form [5], evidenced by Ichigo's striking Zaraki in their final clash. However, Aizen's speed dwarfs that of Ichigo's Bankai [6] and even surpasses that of his Hollowfied Bankai [6 again], demonstrated by his effortlessly outmaneuvering Ichigo in both states. This vastly superior speed grants Aizen yet another edge over Zaraki. ARG3: Mindset Aizen's greater presence of mind will allow him to avoid defeat by carelessness. Aizen exercises great caution in battle, evidenced by his anticipating the possibility of a surprise attack and placing a defensive Kido on his blind spot before the battle began [6]. However, Zaraki exercises very little caution in battle, accepting severe injury as the price for a good fight [2]. This difference in care and caution will be a crucial factor in Aizen's defeating Zaraki. Furthermore, since Aizen is aware of his one weakness in this battle - severe head trauma (see R1) - he will place the same barrier to protect himself as he did in the aforementioned battle with Ichigo. Given that this is his sole weakness, Aizen is actually likely to place multiple of these barriers around his head so as to further protect himself from injury. While Aizen did lose some of this caution due to the Hogyoku's increasing his power [1], he has acknowledged this fault of his. Given his extremely keen tactical mind, he will be very mindful of this error while in battle with Zaraki and thus take care to avoid overconfidence, despite his advantages over Zaraki. ARG4: Nnoitra Viewing the third and fourth of the above videos [7][8] will show that even an unmasked Zaraki was severely injured in battle with the Fifth Espada, Nnoitra Gilga [9]. While Zaraki was clearly superior to Gilga, Gilga was only the fifth of Aizen's Espada, all of whom he is stronger than [1]. The fact that Zaraki had trouble defeating Nnoitra, whose power Aizen dwarfed, indicates Aizen's clear superiority. ARG5: Variety Aizen's greater diversity of techniques and abilities grants him yet another edge over Zaraki. Zaraki may be extremely skilled in swordsmanship, raw physical ability, and spiritual pressure [2], but Aizen is also extremely strong in these areas [1]. Furthermore, Aizen possesses tactical brilliance, Shunpo master, Kido mastery, and an extremely strong intellect, none of which Zaraki can even approach his level in. These four fields - tactics, Shunpo, Kido, and intellect - grant Aizen multitudinous options in battle. When one takes into account Zaraki's customary carelessness, it becomes clear that Aizen's vastly superior skills allow him to outwit, outmaneuver, and slay Zaraki. ARG6: Durability Zaraki's durability and stamina in combat are prodigious [2]. He can suffer many grave wounds without even being slowed [8]. This can be agreed upon. However, Aizen's innate pain tolerance combined with his possession of the Hogyoku allow him to surpass even Zaraki's ability to take damage. By viewing the above videos [10] and [11], one will find that Aizen can endure not only a direct hit from Hado 96: Itto Kaso [12], an attack of obviously massive power, and a Hollowfied Bankai Getsuga Tensho without even crying out in pain. In fact, the only noise Aizen made during the course of those two attacks was a grunt of annoyance and a gasp of momentary surprise - surprise which, despite taking a direct hit from Getsuga Tensho, failed to disturb Aizen's composure. He very quickly recovered from his surprise and evaded the next attack. (One should also note Aizen's impressive durability - Itto Kaso only left him mild burns, despite its great power, and a direct hit from Getsuga Tensho left only as much a mark on Aizen as an ordinary slash from Nnoitra did to Kenpachi.) The Hogyoku also very quickly closed Aizen's wound [11], demonstrating impressive regenerative capabilities. In summary, Aizen's strong pain tolerance combined with his innate durability and Hogyoku-induced regeneration grant him superior durability to Zaraki, eliminating a characteristic that is often one of Zaraki's key advantages in battle. ARG7: Adaptation Another important characteristic of the Hogyoku is its tendency to increase the wielder's power in response to physical damage or exhaustion [13][14]. Thus, even if Zaraki does manage to strike Aizen, unless the wound is immediately fatal, the Hogyoku will simply heal him and increase his power even further. Aizen's Hogyoku-induced transformations all possess incredible durability and power [1]. If Zaraki strikes Aizen, but fails to kill him immediately, Aizen will simply grow even more powerful, increasing the gap between himself and Zaraki even further. While the Hogyoku did reject Aizen as its master in the past, this was due to Aizen's being severely weakened in battle with Ichigo [15]. As Aizen has been restored to an optimal state, his renewed power will both cause the Hogyoku to recognize him as its master once again and allow him to subjugate it regardless. SUMMARY: To summarize my points: - Aizen's statistics far surpass those of Zaraki. - Aizen is faster than Zaraki. - Aizen has greater presence of mind than Zaraki. - Aizen is much stronger than a combatant that posed a strong challenge to Zaraki. - Aizen's wider skill diversity grants him an edge over Zaraki. - Aizen has greater durability than Zaraki. - Even if Zaraki does hit Aizen, unless the wound is immediately fatal, Aizen will simply recover due to the Hogyoku and become even more powerful. SOURCES: [5] http://www.youtube.com... Zaraki vs Ichigo video [6] http://www.youtube.com... Aizen vs Ichigo video [7] http://www.youtube.com... Nnoitra vs Zaraki video [8] http://www.youtube.com... Second Nnoitra vs Zaraki video [9] http://bleach.wikia.com... [10] http://www.youtube.com... Aizen and Wonderweiss vs Yamamoto video [11] http://www.youtube.com... Bleach 295 Subbed Part 1/2 video [12] http://bleach.wikia.com... [13] http://www.youtube.com... Aizen vs Urahara and Isshin video [14] http://www.youtube.com... Aizen vs Urahara, Yoruichi, and Isshin video [15] http://bleach.wikia.com...