I wonder is there anything after max the relationship with enemy (I have tested quite a while which I am level 9 now XD)
There is not, yet. 😼
Loved is the max, and it will have some influence on random encounters and some future side quests. Right now the only implemented scene is the mugging in Mardoc, if the outlaws meet you they should leave you alone (but I can't remember if that's locked behind finding the stronghold or not :P).