Which Wulfing did Ecgtheow kill before joining the Geats?

The Wulfing whom Ecgtheow killed was Heaðolaf. The episode explains why Beowulf’s father was forced to leave his homeland before entering Geatish service.

According to the poem’s backstory, Ecgtheow killed Heaðolaf, a member of the Wulfings, during a feud. Ecgtheow’s family could not settle the dispute by paying the required wergild, or compensation for a killing, so he was banished. He sought protection among the Danes, where King Hroðgar paid the wergild and helped end the conflict.

Ecgtheow later joined the Geats and married a daughter of their king, Hreðel. Their son Beowulf was raised within the Geatish royal household. Hroðgar remembers this old debt when Beowulf arrives at Heorot, interpreting the hero’s visit as partly a repayment of his father’s obligation.

Heaðolaf is often confused with other figures from the poem’s dynastic conflicts, including Hrothulf, Herebeald, and Heardred. None of those characters is the Wulfing killed by Ecgtheow.