Post two people who were Friends first and then became enemies.

Ino and Sakura were first best friends..
but later they unexpectedly they had a crush on the same boy (Sasuke)
That made them Rivals.
They are such good looking best friends.. <3

Shinku and Suigintou, from Rozen Maiden. Not only were they friends, but they are also sisters.

Madara & Hashirama (Naruto Shippuden)

they were Friends when they were kids........then they became enemies...........he he eh ehe

even though they are great enemies now.... they still both respect & acknowledge each other...........he he eheh

Lelouch and Suzaku in Code Geass. They were really good Friends since childhood and they continued to be good Friends while Suzaku didn't know who Lelouch had become. However, at the end of the 1st season, he found out and then they were enemies.

Rin and Haruka were friends, but now they're enemies, competition-wise

They used to be bffs :(

Naruto and Sasuke (Naruto Shippuden) were really good and close Friends one-time but (for the most part) became enemies later on as they got older

sasuke and Naruto they were Friends until sasuke turned to the evil side and now they hate each other