Mutually ruinous is a term used to describe a situation where both parties involved suffer severe consequences. There are several synonyms that can be used to convey a similar meaning. These include destructive, catastrophic, disastrous, and fatal. Other words that can be used to describe a situation that is mutually ruinous include calamitous, debilitating, harmful, and detrimental. A mutually ruinous situation can also be described as a lose-lose scenario where there are no winners. Whatever term is employed, the idea behind it is to convey the concept of two parties or individuals facing equal adversity as a result of their actions or decisions.