If you're trying to describe someone who tries to deceive others through cunning, but ultimately fails, there are a number of different words you could use to describe such a person. One term that might come to mind is "bluffer", but there are a range of other synonyms that might be more appropriate depending on the situation. For example, you could describe such a person as a "fraudster", "charlatan", or even a "swindler". Alternatively, you might refer to them as a "deceiver", "imposter", or "pretender". Regardless of the specific word you choose, it's clear that this sort of person is often seen as untrustworthy, and best approached with caution.