The phrase "on one deathbed" is commonly used to describe someone who is near death or close to dying. However, there are many synonyms that can be used instead of this phrase to add variety and express the same idea. Some examples of synonyms for "on one deathbed" include "in their final moments," "on the verge of passing," "in the last stages of life," "drawing their last breath," "entering into eternity," and "approaching the end of their days." These words and phrases all describe someone who is very close to death and can be used to add depth and emotion to writing or speaking about someone's final moments.