You remember that Kong was juggling a woman between his hands and feet while fighting 3 V-Rexes, which are 50ft long and about 20-21 feet tall? He gets pissed that all these puny humans are jabbing him with toothpicks and crushes them easily.
King Kong still had trouble with those three T-Rexes and a T-Rex is about the same mass as an African Bush Elephant which are perfectly able to be killed by inferior spears than what the spartans used and Kong is only marginally taller than a T-Rex at 25 feet. Top it off with peak human to mildly superhuman physicals on all the spartans and Kong gets brought down by sheer weight of numbers. Probably pretty quickly if he gets surrounded and gutted.
Stop watching Jurassic Park and thinking that animals as big as dinosaurs are invincible. ****ing five foot tall cavemen with sharp rocks tied to sticks and big rocks hunted mammoths to extinction.
Also, don't forget he was also hampered by having to hold that lady in his hand: https://imgur.com/a/lrdahFh
Maybe, but the V-Rexes have a mass of 19.4t, an African bush elephant, 'only' 10.4 tons (https://en.wikipedia.org/wiki/African_bush_elephant. So double the mass. Moreover, there are three of them here, not just one. So this is also wrong.
Maybe if one is surrounded - but 3 Bull Elephants, all much more agile, 2x the mass, 50% taller? Not as easy.
He's pretty fast and agile himself. And sheer weight of numbers? Here he lifts (and throws) a V-rex with one arm: https://imgur.com/a/pxc5j3b
Remember, they weigh 19.4tons. Let's round down - what's 400kg (881lbs) between friends? - to 19 tons. That's nearly 200 humans at ~90kg each (actually 211, but I rounded down assuming these humans are more muscular).
Kong is casually lifting and throwing the equivalent of 200 men with one arm, whilst holding onto a prized possession in the other.
They only managed to kill the Persian war elephants because they had the cliffs, the elephants were clumsy, and the ground was slippery. None of which they have here (not to mention Kong is far more mobile than the elephants).
if 300 spartans accurately throw 300 spears at kong's vital areas immediately when the battle starts, they will win. if the spartans don't do this, and allow kong to bumrush them, they will lose.