In Norse mythology’s Ragnarök, which god kills the giant Surtr?

In Norse mythology’s Ragnarök, no god is said to kill the giant Surtr.

Surtr is one of the catastrophe’s principal destroyers. The surviving accounts describe him fighting Freyr and later setting the world ablaze, but they do not provide a canonical account of a god killing Surtr. The fire giant’s fate is therefore left unstated in the main narrative.

This point is easy to confuse because several major opponents do die in combat. Odin is killed by Fenrir, Thor kills Jörmungandr but then dies from its venom, and Freyr is killed by Surtr. Heimdall and Loki also kill one another.

Some modern retellings give Surtr a more complete ending or have another character defeat him. Those additions are adaptations rather than a consistent detail from the principal Old Norse sources. The safest canonical answer is that no god kills Surtr.