Can “a dead end relationship” be used for other relationships, not just for a romantic one?
Yes, it can. It is more commonly used towards romantic relationships, but can also be used towards close-knit relationships, such as a friendship and sometimes even a work relationship. This is a negative connotation and is implying that the relationship is unhealthy and is not moving forward/progressing. Here are a couple of examples: Ex: Our friendship is a dead-end relationship. You never want to spend time with me, you are always ignoring my calls, and you only want to go somewhere when I am paying the bill. Ex: I can't believe it. This working partnership is a dead-end relationship. I do all of the work for our business and you do nothing!