Suggested by Destroyer Tanjiro is a strong swordsman with a lot of technique and speed on his end. I would also say his durability feats are really pretty great because the guy takes a ton of hits and keeps on ticking. Not just anyone can pull that off but at the end of the day what is going to hurt him here is the massive gap in physical ability. Gajeel is in a completely different league with attack power as well as speed so that removes Tanjiro’s main attributes. His sword also would have a hard time cutting through Gajeel’s armor. Gajeel wins.