A "contentious relationship" refers to a situation in which there is constant disagreement, conflict, or tension between two or more people or groups. It implies that they often argue or have difficulties getting along. Full definition
The board will likely now have trustees that are willing to hold charter schools accountable, looking to bridge contentious relationships with local school districts. (stoprocketship.com)
When you combine that with already contentious relationship between opposing parties, that can be a recipe for disaster. (lawyerist.com)
I want these kinds of contentious relationships in the paintings. (huffingtonpost.com)