Siegfried vs Achilles

[BitVyper]

And to be clear, this is the "invincible-except-for-one-tiny-spot" versions of both.

[big_adventure]

Achilles seems to be overall the superior combatant. His feats from the Illiad are insane once he got motivated (Message from Priam: "thanks, Patroclus, you douche"). Dude fought alone against an entire army, killing so many that it damned up a river, he did it in a day, and he did it without taking a scratch. He trivially slaughtered Hector (by far the best warrior on the Trojan side for the majority of the conflict, only Aeneas was even in his post code), and dragged the dude's headless corpse around the city of Troy. All the while, none of the other Trojans dared challenge him. People who beat gods in combat (Ares is still pissed at Athena here, I think, and Aphrodite and Apollo aren't really happier) and other great warriors universally acknowledged that he was better than any of them - Diomedes, Ajax, Odysseus.

[BitVyper]

Well, Siegfried fought and killed a dragon, and he was able to toss boulders around. Plus he wrestled a valkyrie into submission twice.

[Gordon]

Dude fought alone against an entire army, killing so many that it damned up a river, he did it in a day, and he did it without taking a scratch.

Asteropaeus does manage to slightly wound Achilles in Book 21 of the Iliad. Doesn't slow him down at all, to be sure. Astraeropaeus don't live too long after this.

So he spoke, challenging, and brilliant Achilles uplifted
the Pelian ash, but the warrior Asteropaeus
threw with both spears at the same time, being ambidextrous.
With one spear he hit the shield but could not altogether
break through the shield, since the gold stayed it that the god (Hephaestus) had given.
With the other spear he struck Achilles on the right forearm
and grazed it so that the blood gushed out in a dark cloud, and the spear
overpassed him and fixed in the ground, straining to reach his body.