If a creature is dropped on a monster, how much damage does each of them take?

If a character who was under the effect of a growth potion (double their height and eight times their weight) and weighed 2,400 lbs. was able to use Dimension Door to teleport 400 feet or more into the air, directly above a Huge-sized monster, and fell on it, how much damage would the falling creature – and the monster – take?

I would assume both would take the 20d6 max for the falling over 200 feet, but is there a estimation on additional damage for the falling creature’s size?

According to the splat calculator, at 500 feet you’d be falling at 196 km/hr, and it would expend 1.6 million joules of energy, the equivalent of over 3,000 mid-sized cars hitting an object at 60 km/hr.

A 2,400-lb. barbarian falling 500 feet is like dropping a mid-sized Toyota Corolla off a 50 story building onto a monster – it should do some damage.