This is the 15435th most frequent Russian word.
предательство
Betrayal or treachery.
Here the word 'предательство' is used as a noun, indicating an act of betrayal exhibited by a friend.
Предательство друга — это одно из самых болезненных переживаний.
Betrayal by a friend is one of the most painful experiences.
In this sentence, 'предательство' remains a noun and represents the act of treachery which is unforgiven by the subject of the sentence.
Она не смогла простить предательство даже спустя годы.
She could not forgive the betrayal even after years.
The usage of 'предательство' emphasizes the concept of betrayal as something to be avoided within interpersonal relationships.