To tell briefly, It is only Prussia that dislikes Russia. The reason for this is because Prussia technically represents East Germany, which for a time was taken over by the Soviet Union(Represented by Russia in Hetalia.). This being so, Prussia was stripped from living in the safe custody of his brother(Germany) and for an amount of time lived with Russia(Russia and Prussia had a very abusive relationship), until the Berlin wall fell, which is when he returned once again to his dear brother. This is also why Prussia calls Germany "West", for Prussia is "East". Russia in turn has no feelings against Prussia, and wishes for him to join him again.
However, most of this is interpreted from Fanon, and little of this is supported by Hidekaz Himaruya's character notes, so please stay tuned for more information.