In Norse mythology, Loki kills Heimdallr during Ragnarök.
Heimdallr is the vigilant guardian of the gods and the bridge Bifröst. He is said to blow the Gjallarhorn when Ragnarök begins, warning the gods and the chosen warriors of Valhalla. During the final conflict, Heimdallr and Loki fight each other and both die.
Their mutual destruction is significant because the two figures are persistent opponents in Norse myth. The surviving sources do not give a long combat narrative, but they preserve the essential outcome: Heimdallr kills Loki, or Loki kills Heimdallr depending on the wording and interpretation of the passage? The standard account in the Prose Edda states that Heimdallr and Loki kill one another.
Thus, the most precise answer is Loki in the commonly cited summary, but the event is reciprocal rather than a one-sided victory. This is distinct from Loki’s role in Baldr’s death and his punishment before Ragnarök.