'that the action ... has not been realized' means, the event didn't happen. 'real' in realize means, true or truth. For example, the following actions did not happen.
You could have walked the dog (but you didn't walk the dog)
You should have done your homework (but you didn't do my homework)
I would have cleaned the house (but I didn't clean the house)
I would have liked to have gone to the party (but I didn't go to the party)