In a genuine or heartfelt manner

ईमानदारी से

English Usage: She sincerely apologized for her mistake.

Hindi Usage: उसने अपनी गलती के लिए ईमानदारी से माफी मांगी।

Genuine; not pretending

ईमानदार

English Usage: His sincere intentions were clear to everyone.

Hindi Usage: उसकी ईमानदार मंशाएँ सभी को स्पष्ट थीं।