User blog comment:IamJakuhoRaikoben/Chapter 326: Natsu vs. Rogue, Review./@comment-112.198.77.189-20130406081457/@comment-121.54.8.130-20130406112717

Natsu always had help from his friends or other people of the major enemies that he faced and defeated. The only enemies i think he was able to defeat alone was Erigor of Eiesnwald, Bora, Zalty (Ultear in Disguise, not in full power), Hughes of Edolas, and Sting and Rogue in GMG.

The others: 1. Gajeel (Rhantom Lord Arc) - with aid from Lucy (Sagittarius) 2. Jellal (Tower of Heaven) - Erza wounded Jellal in the abdomen so he was not able to cast Abyss Break. 3. Laxus - with Gajeel 4. Cobra - with Happy 5. Master Zero - with power up from Jellal 6. King Faust - with Gajeel and Wendy 7. Zancrow - with aid from Makarov 8. Master Hades - with Erza, Lucy, Gray, Wendy, Laxus, and Exceed Squad (destroyed Hades' Heart)

Natsu mostly delivers the final blow

P.S. - Natsu was not able to beat Ultear in Tenrou Island Arc.