Chi is a life source energy that can be used defensively and offensively. So yes Superman should be affected by it no matter what.
False. You are talking about the 2005 arc titled the Question? Where Lex Luther builds a machine to gather chi energy and use it to kill Superman?
You should seriously read the comic buddy. Superman is not weak against Chi itself. Superman in that comic actually tanked a chi blast like nothing happened.
Also, the plot to kill Superman using the Chi wasn't about building up massive Chi energy to blast at him. The point of gathering the Chi energy was to give it to a magic user called a Psychopomp who could compel Supermans soul itself with that power to go to eternal torment. The only reason why this was possible was because Superman at one point in time died already. Superman vs Doomsday.
Psychopomp is a spiritual guide to the next world. They are known in history has angels, demons, deities, or a person that walks between both worlds. Like the Question or Phantom Stranger for example.
Chi is not special in DC comics. Characters like Zantanna, Constantine, ect all use chi to preform magic. The Chi itself does not harm Superman. Even Superman himself has chi energy in him. A Lifeforce energy. Only Supernatural energy can harm Superman. Magic!
Lex Luthers plot with the science spire was to gather all the chi energy and let Psychopomp command Supermans soul out of him and send him to a living hell where he would suffer torment for eternity. That was the plot. And it failed thanks to the Question who killed the Psychopomp before it he could even use it.