Rival
Countries can declare their hostility towards other countries by declaring them as Rivals. Countries have some additional hostile actions against their rivals, like the ability to fabricate a Casus Belli and the option to intervene in their Wars.
A Rival Country will not accept friendly Treaties like Alliances, but Countries with common rivals will have an easier time signing Treaties between them.
Rivalry is not reciprocal, meaning that it is not necessary nor automatic for a Country to rival back the ones that have rivaled it. A Country that has declared another as its Rival is known as its Enemy.
Only Countries with similar Great Power Score and not very good Opinion can be declared Rivals, and the maximum number of Rivals a Country can have depends on its Country Rank.
No links to other concepts.