Yes, that works for me, but you should use "was" rather than "is". You are talking about something that has happened, not something that is happening. However, feckless is not a word that I have used that often. I would probably use a more popular synonym such as: His irresponsible behavior / lack of planning / ineffectiveness / reckless decisions/ , made our company bankrupt. It was the final nail in the coffin. Another synomym for final nail in the coffin is: It was the straw that broke the camel's back! Rather than saying that he was the final nail in the coffin, I would tend to say "It was the final nail in the coffin." Your existing comment works and would also be understood though :-) Best Regards Dave