1. Acnologia is the Self- Promulgated Dragon Emperor-
Acnologia was used to be a human who used his Dragon assassinating powers so much that he got turned into a Dragon himself. His monsterous powers was without equal for over four hundred years. He was known to demolish whole nations at will and even the most powerful of Dragons were cautious of him.
As his ascribe was Magic itself, Acnologia was nearly invulnerable. Human could rarely took risk to stand against him and were scared by the mere mention of his name. Acnologia had killed nearly all the other Dragons in the world as a testimony to his great power.
2. Fire Dragon King Igneel is very proud and has the capacity to back up his Ego-
Igneel was known as the King of the Fire Dragons, so one we can be sure that he has awfully powerful. During a few hallucinations in the series, appreciators saw that he was a bit on th haughty side and could only surprised what this Dragon has capacity and what he was capable of. When he appeared, fans finally saw that Igneel was a massive Dragon and his face to face battle with Acnologia fully proved his capabilities. While other Dragons were known to run off from Acnologia, Igneel was the only one anxious to fight him. His firepower makes Natsu's look like a parody or joke.
3. Irene Belserion is a human who transformed into a dragon with great Abilities-
Initially Irene was a human and during her time, she was known as the Dragon Queen. She used her witchcraft power to give humans the powers to tack Dragon assassinating powers, so she was also known as the mother of all Dragon Slayers.
She's very powerful, able to enchant whatever she sees fit. During her fight with Ezra Scarlet she easily call for a massive meteor as a testimony to her powers. Her powers to fight as a human and a Dragon like Acnologia gives her a great edge over any enemy.
4. Atlas Flame is a humble and kind Dragon with Cosmic and immense Powers-
Atlas was first instituted as a antagonistic enemy to humans because he was under the impact of Dragon Predominance Magic. Fans were surprised to find out that he was initially good friends with Igneel and Natsu was glad to call him his uncle. During his fights, one could see just how much powerful this Fire Dragon was.
His body was made solely of flames, which made him defensive to even the most powerful attacks. Atlas Flame was known as a god by a village of giants, and when the whole place was frozen over, he easily melted all the ice and saved the people with but a piece of his soul.
5. Metalicana is an Iron Dragon with a Sturdy hide-
Metalicana is a Dragon of totally different type that taught Iron Dragon Slayer Magic to Gajeel, and concluding by just how powerful Gajeel is, it's clear that Metalicana is much more powerful. As an Iron Dragon, Metalicana has a very strapping hide that's likely more long lasting than that of most other Dragons, which makes him a intimidating enemy. He showed up along with other Dragons to save human life from Tartaros.
6. Weisslogia is a white dragon with Worldly Power-
Weisslogia is a kind Dragon who bought up Sting as his own son. He taught Sting his designation label of dragon slayer magic, which is both powerful and worldly-wise . One can judge his brawn based on Sting's skills because he taught Sting all he knows. His stigmata is capable of disable his enemies and his breath attack is more like a fatal laser beam. Just Like Skiadrum, Weisslogia also owns the ability to rewrite memories of a human, which he did to Sting.
7. Skiadrum the Shadow dragon the sign of darkness-
Skiadrum is a Dragon who looks just as dark as a shadow — so he got the name Shadow Dragon. Just Like Grandeeney and Igneel, Skiadrum also transported to the future through the Eclipse Gate with the expectations of obtaining enough power to knock Acnologia. Everything Rogue knows about Shadow Dragon Slayer Magic, he got to know from Skiadrum.
He owns the distinctive skills to operate any human's memory, just as he did with his son Rogue. This allows him to create memories in the human mind which either had never happened, or he can change the content of the memory completely. Power like this should be frightening.
8. Grandeeney the sky Dragon employs the wind in combat-
Sky Dragon Grandeeney is more tender-seeming than other Dragons, but that doesnot really mean she's weak. Though she'd much rather ignores a fight, she has no problem showing her power when the conditions calls for it. She was one of the few Dragons that traveled forward in time to defeat Acnologia, and since she employs the wind in fight, she has a great lead over any Dragon. She also brought up Wendy Marvell to be a very powerful Dragon killer.
9. Animus became the king of Stella by using his powers-
Animus suffered a ghastly destiny at the hands of Acnologia, but even when he was near his end, he had power enough to accomplish the Dragon Soul Technique to pack himself in Sonya's body. Animus is able to do different things with his Magic: he was able to operate Sonya's mind and produce a false image of himself which Sonya could see, and he can also bind someone in place by just pointing in that direction. His breath of light is a gigantic beam of pure energy.
10. Motherglare was strong enough to give Atlas Flame a very hard retaliation-
She had came through the Eclipse Gate with other Dragons at the instructions of the evil Rogue Cheney, who used Dragon Tamer Magic to have Dragons do his auction. During this fight, Atlas Flame got to know Natsu as Igneel's son, turned on Rogue, and take measures to take down Motherglare. She held her own against Atlas Flame for a very quite long time and even managed to get some good hits in on the Fire Dragon. Motherglare is capable of laying a large number of eggs, which hatch quite fast and in battle ground can fight multiple enemies.