Left heart radical (Kangxi #61
心 in its 3-stroke compressed form). Anchors the emotional weight:
惨 is the heart's response to suffering — tragic, miserable, wretched, ghastly (
悲惨 tragic,
凄惨 dismal,
惨叫 a horrified scream). Same radical groups all heart-feeling verbs:
怕 (fear),
怪 (strange),
忙 (busy),
慢 (slow).