If Yami landes his Dimension Slash, Natsu loses. Otherwise, Natsu have shown better feats. Also, according to FT verse, Dragon Slayer Magic > Normal Magic, so maybe Natsu wins here. Just a possibility!!
Naruto characters have ki but can’t use it correctly
Ki is lifeforce when Guy access all 8 gates he begins to use his lifeforce as fuel as such ki in Naruto does exist and can be used as a weapon but they don’t have the proper training to use it effectively as they literally kill thenselves
Ki is the best option and could potentially be the most versatile as it’s full array of uses is unknown currently.
Many anime have ki as their main power source. Even for anime like Nanbaka, where ki's not a major power-system.. and only few people use it.
In Nanbaka, we have seen drawbacks of using ki.. so it's not versatile.
Plus, you might know the drawbacks of opening Gates in Naruto-verse...
And it's life-force we're talking about here. Like we're projecting our life force as attacks....
If you've seen MHA , you might remember in Season 4 I guess, when they went to save Eri, some villian had quirk which drains life force. And it made heroes fatigue.
So, you might get now how dangerous is projecting ki out of our body..