Our closest cousins on the evolution tree, Neanderthals, face off with a croc from the Cretaceous, Mahajangasuchus.

Size:
Neanderthal: 1.7 meter tall
Mahajangasuchus: 1 meter tall, 3 meters long

Strengths:
Neanderthal: Intelligent, use of stone tools, heavily built and resilient to damage
Mahajangasuchus: Crushing and slashing jaws, armored skin, tail acts as a blunt weapon

Weaknesses:

1 meter tall, 3 meters long

Strengths:
Neanderthal: Intelligent, use of stone tools, heavily built and resilient to damage, work in family groups, often tackles large prey
Mahajangasuchus: Crushing and slashing jaws, armored skin, tail acts as a blunt weapon

Weaknesses:

Neanderthal: Relatively weak when compared to most animals, skin and clothes provide little protection
Mahajangasuchus: Unintelligent, must get close to injure the Neanderthals, best suited to the water.

Since a single Neanderthal wouldn't stand a chance against a mahajangasuchus, I'll have four of them against one croc while on the croc's home turf.

Battle:

100,000 years ago, a hunting band made up of an elderly Neanderthal and his three sons trek across the frozen landscape that will one day become Germany. Many of the large herbivores they prey on have moved south for the winter, except the woolly rhino which they seek. They dragged along a sled capable of carrying dozens of pounds of meat, but on a hungry stomach even an empty sled is heavy. They've been searching hours and haven't found a sign, but they refuse to go back to their cave emptyhanded. As the eldest son scans the scenery, he spies a bizarre object that seems to capture the sun's rays.

The hunters make their way towards the sphere cautiously, poking their spears into it, and feeling it hit nothing, the father puts out his hand to touch the sphere, before walking into it. The rest of the hunting party grunt and converse about the disappearance of their father. After a few minutes, which felt like forever, they gather their courage and follow in search of the missing hunter. They emerge into a very different world, dry and hot. Meer feet from them, they spot their father enjoying a drink from a pond. "Look sons," he said, "game, water. We could make a home here." As they squinted in the sun's rays, they were taken aback by the bizarre creatures about. Lumbering beasts with the bill of a duck, and hairless rhinos with three horns. As the man from the lake walks towards his friend, the water erupts. A massive pair of jaws crunched into his waist as he screamed in shock and pain.

The croc-like beast had never seen animals such as these hairy bipeds, but food was food. Used to crushing the bones of giants, the Neanderthals hips and pelvis were pulverised by the massive jaws and conical teeth of the croc. He knew that even if he survived that he would never walk again, that doesn't mean he couldn't take the reptile down with him. With stone knife in hand, he began to rapidly stab at the croc's muzzle, like a wasp stinging a threat. It certainly hurt, but the mahajangasuchus was used to feisty prey, and knew that it's struggles would cease if it got a lungful of water. It turned around and started to lumber back into it's lake, when just as it was about to begin drowning it's prey it felt several things grab it's tail and hind legs. The Neanderthals companions rushed to their clanmates aid, preventing the croc from returning to it's lake and began to drag it back onto shore.

Dropping its quarry, the croc turned its head around and grabbed the leg of one of its assailants. It was not a crushing bite, but a gripping one as he threw the ape with the turn of his massive head and tossed him into the lake. The eldest son dropped the tail as the croc tossed his brother, and leaped for the head, wrapping him muscular arms around the jaws of the croc, screaming "Kill it! Kill it!". The fourth Neanderthal dropped the hind leg to pick up his spear but was met with the tail of the mahajangasuchus striking his face, sending him flying to the shoreline. As the mahajangasuchus thrashed, he could not open his jaws. While his bite force was strong, the muscles to open his jaws were minuscule when compared to the Neanderthals arms. It bucked, writhed, and spun to escape the ape, the Neanderthal's grip held true and couldn't not be dislodged.

Seeing no other option, the mahajangasuchus began its way towards the water, hoping to dive and drown its assailant, or force it to flee. As it lumbered towards the lake, it passed by its original victim, the now crippled old man. As the old Neanderthal saw the beast trying to escape, he gripped his stone knife tightly. This croc had crippled him and harmed his sons, he will not let this offense go unpunished. With adrenaline in his veins he quickly intercepted the crocs path, grabbing onto its underside and began stabbing and slashing at its throat and belly. The croc may have cried out in pain if he was able to open his great jaws, but the only sound it could muster was a low, dignified growl that sputtered with blood as the old ape continuously stabbed the throat. As the croc collapsed, the old Neanderthal continued his assault, as his sons the eldest son grabbed his own knife and began stabbing it in the head and eyes. After a few moments, the creature's tough hide was nothing more than a quilt-like pattern of bloody holes and scales. The two younger brothers, one with gashes in his leg and the other missing several teeth staggered back to their father and older brother.

The brother missing teeth began to butcher their kill for transport as the eldest tended to the youngest brother's leg. When that was finished, they turned to their crippled father to carry him out of this place. "No sons," he said, "'my life is done. Get meat back to clan, I will stay. If I am to die, I will die warm". The brothers loaded the flanks, limbs, tail, and head onto their sled, bid their father a tearful goodbye, and re-entered the shining ball into their frigid home territory. The father's sacrifice was not in vain, as the meat came at the time the clan needed it most. With his bounty of food, they sat out the rest of the winter in relative comfort until their territory was once again filled with large herbivores. The skull of the great beast was the prized treasure of the clan, used to tell stories of the legendary chief who slayed the beast with his sons. However, the Neanderthal stories grew quiet and the skull decayed. Both were lost to the passage of time.