The term 'HIGHEST HEART' can be solved by the crossword clue 'ACE' (3 letters). The term 'ACE' is a noun that is used to describe someone who is exceptionally skilled or successful at something. It is also used to refer to someone who is the best or most highly regarded in their field. In this context, 'HIGHEST HEART' could be interpreted as someone who is the most highly regarded for their kindness and compassion.