Which argument type is represented by claiming that past promises, unfulfilled, indicate a lack of credibility?

The argument type that suggests past unfulfilled promises indicate a lack of credibility relates to the assessment of someone's reliability based on their previous actions. This approach is focused on evaluating a person's past commitments and outcomes to cast doubt on their current credibility or trustworthiness.

By considering someone’s history of promises that were not fulfilled, the argument effectively discredits their ongoing claims, aligning with the definition of disproving a minor point. This strategy is employed to reinforce skepticism toward the subject's current statements or intentions, asserting that their previous failures render them less trustworthy in the present.

This argument does not redirect to unrelated topics (which would be a diversion), nor does it rely on a question intended to guide towards a particular answer (leading question). Additionally, it isn't a personal attack on the individual that would categorize it as an ad hominem. Thus, the justification rests on the idea of evaluating credibility through the lens of past actions, making the focus relevant and reinforcing the concept of disproving a minor point.