This is the 8914th most frequent Japanese word.
残忍
Cruel; brutal; ruthless.
In this sentence, '残忍' is used as an adjective describing the cruel or brutal actions carried out by the perpetrator, focusing on the negative traits of cruelty.
その犯人は残忍な行動をとった。
The perpetrator acted in a cruel manner.
Here, '残忍' is treated as a noun referring to the concept or definition of cruelty or brutality in a general or abstract manner.
残忍の意味を辞書で調べてみました。
I looked up the meaning of '残忍' in the dictionary.
'残忍' in this case acts as an attributive adjective to illustrate that certain aspects of a person's thoughts exhibit cruelty or brutal characteristics, giving insight into their nature.