sincere

I gave my brother a sincere apology after I accidentally broke his favorite camera.

(Chinese) 我不小心弄坏了哥哥最喜欢的相机后，向他诚恳地道了歉。

The candidate made a sincere promise to improve the local schools if elected.

(Chinese) 候选人做出真诚承诺，如果当选将改善当地学校。