1. Hatake Sakumo
Said to be a genius and famed as Konoha's White Fang. It's supposed that he was stronger than the Sannin too. He seem pretty awesome.
2. Hozuki Mangetsu
The strongest and most feared of the 7 Swordsmen. Mastered the use of every sword and most deadliest with Silent Killing. Would love to see him use every sword at once.
3. Orochimaru
Worthy of mention, hyped to be a really scary person. And even hinted to be really powerful, though he got a lot of screen time, we need more action.
4. Hiruzen
Hailed as the strongest Hokage who ever lived, and nicknamed the God of Shinobi. Too bad he died when the power scaling was really low.
I was with you until 3-4, number 3 seems to be a fan boy thing, orochimaru has had plenty of screen time it seems like a fan boy thing to want more, I thought this list would be a tad bit more fair. 4 please don't be one of those hiruzen hypers, Hiruzen already got screen time in the manga against juubito but the power gap was too large and hiruzen is not stronger than the first so juunito was stronger than the first therefore Hiruzen can't get proper screen time unless he does something with hagoromo.
A fairer top five list would be
1.Kushina:I think we all know kushina is a strong woman but her abilities have never really been explored in depth we all have snipers of such power.
2.Ashura:ik ik Naruto is ashura but you never know if ashura himself had other abilities Naruto has yet to explore in depth, such as the chakra beasts.
3.Indra: a good question is does indra have all mangekou special abilities as do all mangekou abilities stem from him, we've seen susano but that's pretty much all we know.
4:Hamura:Sages brother, got literally no battle screen time, enough said.
5:Hagoromo:We still can't testify how powerful this guy is I mean sure there's Naruto but sasuke us the yin but showing like zero stuff. So it'll be nice to see him do things.
Sub category
1.all tailed beast jinchuriki's:I think each jinchiriki's combat abilities needed to be explored ino, besides Naruto, bee, and gaara, and possibly utakata but everyone else needs to be explored.
2.Negato

ude had screen time but the full extent of the devastating power the rinnegan had wasn't really explored in great detail in my opinion.
3:Kabuto:As much as I hate to say it, I don't think kabuto in full extent expressed all of his power that he could have shown I think he was impeded by itachi, if kabuto had a wider area of range I think he could do much much more.
4:Juubito

bito said something about an assault form but we never got to see it so it seemed like he needed more screen time plus I think I would have liked to see his assault form.
5:Juubidara

ude had little feats outside surviving eight gates but that's juubi Jin stuff anyway and casting IT, I mean yes he pulled many strings but power feat wise not intelligence there weren't that many in my honest opinion.