I rarely desire to be intentionally mean to someone unless they really, truly hurt me. The problem with having Fi combined with Ne is that I usually don't talk things out with people, and I try to "read" between the lines of what the person said or did. And when someone wrongs me (sometimes unintentionally), it hurts me deeply.
What's worse, I hold grudges. Little doubts about people's actions grow and nag me. If you cause me enough pain, I will, quite frankly, be unable to forgive and forget. I'll try to read into the situation from countless different angles.
Why did you do it? Was it me? Was it you? Will you do it again? I've seen previous behavior that suggested that was coming. Should I forgive you?
It sometimes takes me weeks to forget damage caused by someone I trusted, and that is only because the stresses of everyday life distract me. If I'm alone in my thoughts, sometimes the wrongdoing will jump back into my primary memory, and I'll remember everything about the infraction. I'll remember your face, I'll remember the exact words you said, and I'll feel the same, stabbing pain I felt weeks ago.
That's why an NF can be so mean. We know immense amounts about those we trust and love. That means when we are betrayed by those who hold this sacred position in our lives, the pain is that much more intense.
When lashing out in response to emotional pain, NFs can customize their attacks to be like a spike in the sweet spot. It's a relief to see someone visibly shaken after one of these retaliations. It feels good to know that the world of hurt you feel inside that no one else really understands the magnitude of has been somewhat channeled to the offender.
Problem is, in the "calm after the storm," when you both take a step back and look at each other after the attack(s), then the remorse sets in. I feel bad after making someone tear up with a well-placed, personal attack, no matter how deserving.
Happy NF friend == loyal, caring, kind
Wronged NF friend == hurt, untrusting, sad