[Doctor Stochastic]

What class of organism is overwhelmingly the most successful by any objective standard -- numerous, adaptive, indestructible?

Beetles? More complex than humans, half again as many appendages.

[From many - one.]

Can I play?

My candidate would be class insecta. I'm confident about numerous and adaptive, less so about indestructible. Aphids seem awfully squishy, mosquitoes get eaten at an alarming rate by bats and dragonflies.