I had worked with a guy which is smart, or at least persuasive, since him was hired somehow. He after started working with the team, him complaining about the project proposal, about the bad code decisions and had serious discussions with the product owner. After I talked with the PO, I opened a meeting with the complainer to extend my hand and say that I was opened to listen, him thanks me but preferred to stay a little away. The CTO proposed that since him spotted a bad code (it really was), him had time to analyze better and fix! In the end him lost 2 or 3 weeks fixing the code, wasn't able to finish and request resignation directly to the HR with the reason that the team and the project was bad, probably criticized the CTO. I had to take the code him left and finish the fix!