Dragonite Line: weather control, has human-level intelligence, can circle the globe in 16 hours, rules over a section of the sea.
Tyranitar Line: eats an entire mountain in order to evolve, nigh impervious to attacks, can completely alter the landscape to the point that maps need to be redrawn, has a mega form.
Salamence Line: hurls itself off of cliffs as an infant, tempering its body to be harder than steel, learns to fly. Scorches forests and mountains when angry
Metagross Line: claws can rend through iron with ease, has 4 brains which combined is 'smarter than a supercomputer'
Garchomp Line: scales can cure any sickness, flies at the speed of a Jet to pursue prey, its blades can cut through trees in a single go.
Hyreigon Line: moves from area to area, devouring everything in its path until there's nothing left. Much like a swarm of locusts. Extremely aggressive.
Goomy Line: Slick body repels attacks, its horns act as a radar and can punch with the force of 100 pro boxers. Base form is the weakest of all dragons.
So just going by the Dex entries
Tyranitar > Dragonite > Hydreigon > Salamence = Metagross > Garchomp > Goodra
