The term 'with all one's heart' is an expression that is used to emphasize the sincerity and intensity of one's feelings. The crossword solutions for this term are 'MIGHTILY' (8 letters), 'dearly' (6 letters), and 'DEEPLY' (6 letters). These words all describe the intensity of the emotion being expressed, with 'MIGHTILY' suggesting great strength and power, 'dearly' suggesting a strong affection, and 'DEEPLY' suggesting a profound level of emotion.