"Heartsickening" is a powerful word that is used to describe something that causes one to feel profound sadness or anguish. There are a number of synonyms that can be used in place of this term, including "heartbreaking," "gut-wrenching," "soul-crushing," and "devastating." These words all convey a sense of emotional pain or distress that is intense and overwhelming. Other possible synonyms for "heartsickening" might include "tragic," "disheartening," "melancholy," "poignant," or "pathetic." Whether describing the loss of a loved one, a personal disappointment, or a global tragedy, these words can help to capture the depth of the emotional impact that such events can have on one's psyche.