Explaining how Aizen's Kyoka Suigetsu is an ultimate hypnotism Zanpakuto

What is Kyoka Suigetsu?

It is the Zanpakuto, owned by Aizen which has ultimate ability of complete hypnotism.

Kyōka Suigetsu's most fearsome power is known as Kanzen Saimin (完全催眠, "Complete Hypnosis").

How does it look?

Kyōka Suigetsu (鏡花水月, Mirror Flower, Water Moon): In its sealed form, it resembles a normal katana. The only decoration is the tsuba, which is a hexagon. The two sides parallel to the blade are long, whereas the four sides above and below the blade are shortened, making it into almost a diamond or prism-like shape. It has a green handle.

What are it's abilities?

• Shikai: The release command is "Shatter" (砕けろ, kudakero) and is used to both activate and deactivate
• Shikai Special Ability: The special ability of Kyōka Suigetsu is Kanzen Saimin (完全催眠, Complete Hypnosis). It controls the five senses to the point where it can make the target misinterpret another person's form, shape, mass, feel, and smell to be an enemy's. The initiation condition for the hypnosis is for the enemy to see Kyōka Suigetsu at the exact moment it is released. After seeing it just once, this person will completely succumb to the hypnosis every time it is released, regardless of how long ago they saw it, as the Visored remain affected even after 110 years. When Aizen turns off the hypnosis by force of will, the image shown melts away or shatters. 
  
   The complete hypnosis of Kyōka Suigetsu is absolutely flawless; even if the target is aware of being under the hypnosis, they cannot resist its influence.The hypnotic abilities of Kyōka Suigetsu make it a highly useful tool in combat, for Aizen can create simple or complex illusions to deceive his opponents. For example, by creating a decoy of himself, or other illusions to distract his opponents, Aizen can hide his own movements and attack with impunity. His opponent will remain focused on the illusion until it is too late to react.
• He can create either simple or complex illusions to completely fool or disorientated his opponents. Whilst his foes are concentrating on his illusions, he can then hide his actions with extreme secrecy and impunity, and when he delivers an attack they'll be focused on the decoy until it's too late. While the illusions created by this Zanpakutō can be powerful.
• It's different in Tokinada's case. If the blade is touched, then the entirety of his hypnosis collapses. But in case of Aizen, he still retained his abilities even after Gin de-activated it. Wielded by Aizen, Kyoka Suigetsu is flawless.
  
  
  There are conditions on how to turn off Kyoka Suigetsu-
• First thing, it can't be negated unless you got high reiatsu or unless Aizen stops it manually or commands KS to stop using Kanzen Saimin
  

How can it be blocked by or countered by opponents??

• Answer-By holding Aizen's sword before or sense the real sword after it stabs you while you're trapped in it.

• Illusion removal kido would also work.
•  There's no possible way to stop it 'cuz even Yhwach(that also Soul King absorbed yhwach, who could see future, had almighty, could also alter the future, could also manipulate fate and transcended the soul king itself, who's best feat was cutting a universe in half and creating an infinite timespace, as well as holding all the realms together) got trapped in Kyoka Suigetsu's ability.
  
  
  
  
  
  Hence proved it's possibly impossible to neg the effects if you don't know anything about it.