Amalek is Israel’s prototypical enemy. Or perhaps I should say “was” rather than “is”. That requires a bit of explanation ...
Israel became a nation during its period of Egyptian slavery, so we can certainly number the Egyptians among Israel’s earliest mortal antagonists. But Israel fought no battles with Egypt. At the Red Sea, no Israelite even drew his sword. Instead, God fought for his people, and the nations were awed, just as God had anticipated: “The peoples have heard; they tremble; pangs have seized the inhabitants of Philistia. Now are the chiefs of Edom dismayed; trembling seizes the leaders of Moab; all the inhabitants of Canaan have melted away.”
Who is absent from this list of trembling peoples? Amalek.