Forgive me if I'm mistaking but I assume you mean the most important value one shares with other people(

i. e it's reciprocal), if so then it has to be mutual respect for me, it eliminates contempt and breeds understanding and therefore creates peace, wherever there is peace is fertile ground for love to bloom. Some might argue that it's trust but I feel peace and love exist without trust but with mutual respect it will all crumble, yeah with trust you can gain peace and love but respect acts as the skeleton that holds all the other values in place.