Fe = "You should do this", "Your should stop doing this", "You have done a bad thing and should be punished by me".
When Fe is controlling it pushes its plans and punishes.
Fi = "You are this", "You feel this", "You are a bad person, and I'm going to run away".
When Fi is controlling it withholds and is passive aggressive.
Once again, definitely not hard and fast rules as all types can do all these things, but there is a difference between telling someone what to do and telling someone who they are. There is the added complexity of the person hearing the message to interpret it the other way as well. I'm not terribly pushy, but there have a been a couple of incidents when I told my family someone they should do, and they heard me criticize who they are which never crossed my mind. When they told me who I am, I asked what I was doing wrong.