Superman vs Koishi - Death Battle!

Superman:
You all know him by now. The Man of Steel, the character written by many authors, with the phrase "He is as strong as he needs to be" always thrown around. Such a character is often regarded as overpowered, and rightfully so. So he should be able to rise to any occasion and defeat any foe unfortunate enough to cross him.

But he has weaknesses. Four of them in particular: Magic, Kryptonite, Telepathy, and Red Suns.

Koishi:
Hailing from the land known as Gensokyo, Koishi is born into a race of unnamed Youkai that were exiled into the Underground. Her race, often dubbed "Satori", are mind readers. They have this quality because of a third eye. A mere gaze is enough to be able to tell what anyone is thinking. A powerful Satori is even capable of manipulating one's conscious thoughts, so they can better anticipate a method of attack, or weaknesses.

There is no known method of defense against these abilities, Koishi is further exceptional even amongst her species. Her third eye was closed willingly. It increased her powers exponentially, now capable of reading and manipulating the Subconscious of those around her, Koishi is a force to be reckoned with.

She is able to dig into a person's deepest secrets, render herself invisible to their mind, and perhaps even induce hallucinations and illusions that seem very real to the affected. As a Youkai she is already capable of magic, but she is considered an extremely skilled individual in it's use. Easily included among the strongest magic users in Gensokyo.

THE DEATH BATTLE:
Superman would fare little chance against Koishi. As a Youkai her body has several incredibly strong traits. As soon as Superman manages to surprise Koishi, he would find that his Subconscious is being heavily afflicted. While he does have some level of mental control in order to resist, he still proves an easy prey for Koishi's much greater powers in that field.

Just like that, Koishi would seemingly vanish from the battlefield, she would know his weaknesses, and begin to tear into him. Leaving him little time to cope with the vicious onslaught. Even without Kryptonite or a Red Sun, the battle would prove to be brutally one-sided in Koishi's favor. Considering this is a Death Battle, she would also be certain that Superman is dead, and won't be coming back.

Magic and Telepathy are some of Superman's recognized weaknesses. Furthermore, none of Superman's powers would help him see the now invisible Koishi. To paraphrase a quote from Koishi herself; "Even if your eyes can recognize me, your mind refuses to acknowledge it."

The Winner is... Koishi Komeiji.