SPOILERS!!!!!! If you are not up to the Anime series or Manga!!!
Natsu Dragneel is the Strongest wizard in Fairy Tail. Natsu not only does he get stronger every time he fights a very strong opponent but he is also Zerefs strongest demon E.N.D. Natsu is the definition of Fairy Tail always fighting for what's right and fighting for his family from Fairy Tail. Natsus pure heart is what makes him strong and fighting for Igneels wish to live on even though he is longer with Natsu. This amazing wizard is strong magic wise and heart wise as well.
Natsu is a Fire Dragon Slayer taught by his dragon father Igneel. Natsu has many dragon slayer attacks such as, Fire Dragon Roar, Fire Dragon Wing attack, Fire Dragon Iron Fist, Fire Dragon Talon, Fire Dragon Crimson Lotus, Fire Dragon Brilliant Flame, Fire Lightning Dragon mode, Fire Dragon Lightning Roar, Fire Lightning Dragon Fist, Fire Dragon Mode. So many amazing attacks that there are just too many to put. Natsu is just so awesome.
In the Tartaros Arc. Natsu fights Three different demons from the 9 Demon Gates of Tartaros. The first demon he fight is Jackal who he also successfully defeats. Then during the big battle against Tartaros Natsu begins to fight Tempests while Lucy tried to recover from her fight with Jackal. He sadly didn't finish the fight due to Torafusa's curse magic causing poisoned water to rise and causing everyone but Gajeel to loose cautiousness. Later on Natsu finds out that Igneel has been inside of him the whole time since he disappeared. Igneel busy fight Acnologia then gives Natsu a job which was to retrieve the book Mard Geer had called E.N.D. Natsu then begins to fight Mard Geer along with Sting and Rogue and then Natsu and Gray team up to finally defeat Mard Geer. Before Natsu and Gray begin to argue over the book Zeref comes and takes the book back. Igneel then begins to tell Natsu everything he wanted to know as his final moments of being alive were coming too soon. Natsu see Igneel die right before his eyes and is heartbroken by the fact that he finally gets to see Igneel again only to see him die. This Arc. completely broke my heart for every character who lost someone but Natsu seeing Igneel die was the most heartbreaking scene for me. Igneel dying made Natsu the new string amazing Fire Dragon Slayer he is now and I can't wait to see how much more amazing he can get.