Natsu is back and his intense fire abilities guarantee that he will put up an excellent fight! Train’s gun is virtually unbreakable and his Railgun should deal a lot of damage. Natsu’s speed is great, but he will have to let up eventually and one hit from the Railgun is all that Train would need. Keep in mind that Train is a high above of course. This would be a fun long range battle. Train wins.
Update 8 7 2020 I’m afraid Train won’t be able to keep up. Natsu wins.