The battlefield runs red with meerkat blood. Half of them get trampled the other half end up as polar bear poo.
Lions destroy the T-Rex, they can jump high enough to get on his back and it's a wrap from there, once the T-Rex falls, the Lion pride leader looks to the sky, roars and says, "Tonight We Dine in Hell!!!"
As for the crab, if it is just a giant version of a crab, at first I want to say the crab due to it's claws and aggressively defensive nature. However, we must remember that though giant, this is a crab, the elephant charges, the crab raises it's claws too high to attack the elephant's head and ends up flipped over on it's back. Game over for the crab, the elephant takes it's time stomping the life out of the crab, mothers cover their children's eyes, souls are changed, it's an ugly brutal display of nature.
Now for mine, this is one that has always perplexed me.
One silverback gorilla, or 10 vintage Mike Tysons in their prime. The Tysons would be attacking all at once with full aggression, zero fear, who would win?