"Open-heartedly" is used to describe someone who is acting with sincerity, honesty, and fullness of emotion. Synonyms for this word could include "wholeheartedly", "genuinely", "sincerely", "freely", "unreservedly", "candidly", "frankly", "honestly", "authentically", "transparently", "truthfully", and "without reservation". Each of these words speaks to the idea that the person is fully engaging with their emotions and showing their true self to those around them. Whether you are describing someone who is openly expressing their feelings or acting with integrity, there are many synonyms for "open-heartedly" that can help you communicate this powerful concept.