The Bible is full of these, most notably Samson slaughtering 1,000 Philistines with the jawbone of an ass. (There's an interpretation that this actually describes an army under Samson's command making a pincer movement that looks like the jawbone of an ass, but that's not as fun.)
The Ten Plagues of Egypt were essentially the Hebrew God curb-stomping a series of Egyptian deities.
After the Israelites refused to enter the Promised Land because they were afraid of the Canaanites, God became angry and told them that none of them would ever enter the Promised Land, but only their children would. When they changed their minds and tried to enter the Promised Land after all, they got curbstomped.
Jesus at the battle of Armageddon in the book of Revelation, in Game Breaking fashion. As the Left Behind book Glorious Appearing can tell you, His enemies don't stand a chance against Him.
Justified example, given how Jesus is the son/human incarnation of GOD — you'd be hard-pressed to not be curbstomped by that.
On one side, we have Jesus the son of God. On the other, a man possessed by 5,000 demons named Legion. Legion never stood a chance.
The story of David vs. Goliath, wherein a fully armored giant champion is killed by a 13 year old with a weapon used to kill pests, and the boy then decapitates the giant with the giant's own sword.
Slings can actually be lethally accurate against an armoured opponent (a sling stone may have the same kinetic energy as a pistol bullet) and Goliath did the classic mistake - underestimating his enemy. David had, despite his young age, already killed a bear and a lion, which were far more dangerous opponents.
Norse Mythology has these in just about any battle involving the thunder god Thor. His battles against giants typically last only one hammer throw before the giant is defeated. The only exceptions tend to be when Thor is without his hammer, the opponent uses magic, or he's fighting the Midgard Serpent.
In The Kalevala, Hot-Blooded Joukahainen challenges age-old Väinämöinen in a Wizard Duel, which proceeds by literally comparing what they know about the world. The old guy lets him have his fun for a while, until Joukahainen claims he was there when the world was being created. Which is something a youngster doesn't say to the guy who actually was there. So, yeah. Väinämöinen doesn't even need to do any stomping, he just sings a song that makes the earth swallow his enemy up, and Joukahainen only escapes by promising his sister's hand.
Hindu Mythology is replete with legends of gods and heroes killing thousands and thousands of enemies by shooting multitudes of arrows.