彼の不誠意な態度に失望した。
I was disappointed by his insincere attitude.
会社側の不誠意な対応に、被害者たちは強く抗議した。
The victims protested strongly against the company's insincere response.
約束を何度も破るのは不誠意と言われても仕方がない。
If you break your promises again and again, you can hardly complain when people call it insincerity.