Can a bleeding ulcer cause a fatality ?

Yes: Fortunately it is rare that a bleeding ulcer is fatal, but certain circumstances like if the patient is taking blood thinners, or has liver problems, like cirrhosis, or is far away from medical care, could cause a bleeding ulcer to be fatal. Almost always, bleeding ulcers can be treated successfully by gastroenterologists doing a scope.

Yes but rarely: It is unusual for a bleeding ulcer to be fatal today. We have many ways of controlling the problem today. It occurs singly in the string of other severe prelims such as liver or renal failure or someone who has a clotting problem that is genetic or drug induced.