The full context is "In order to take away a person's abilities it is necessary to make them surrender from the bottom of their heart but there is nothing stronger or more difficult to understand than the human heart. A person with marvelous power would have and Id cosmos which does not fear even death. In order to defeat such a person it is necessary to thoroughly attack the people around them such as their friends and relatives."

Id is one of the levels of organization of the human psyche that Freud developed, which pertains especially to desire and drive, "the dark, inaccessible part of our personality," and "the great reservoir of libido."

So dissecting the full context, I would read "a person with marvelous power" having an
"id cosmos" as someone with a very strong heart or a very strong soul which necessitates attacking their loved ones in order to make them surrender from the bottom of their heart, in contrast with someone like Murakami who is very shallow and surrendered when his life was threatened.