Simple enough question I suppose, But asking anyway.
Which Legion particularly hates what other legion?
Thousand Sons probably have a particular disliking for Space Wolves, while Dark Angels probably see their issues with the Space Wolves as more of a friendly Brotherly rivalry.
I assume also that the Iron Hands are probably not big fans of the Emperor's Children. I believe Ferrus Manus thought Fulgrim was a bit of a pain in the neck.
What other rivalries are there and am I correct about the ones above?
Also, why do they hate/dislike/compete against each other?
Please note; This is the background forum, so I am looking for background info. Don't just say, Legion 1 hates Legion 2. Tell me why they hate each other. What happened that made this rivalry more than just, "You turned on the Emperor, your a traitor".