Well is Hashirama at his strongest? Hashirama at his strongest had Bijuus 2-9 under his control; some people doubt this but it's not that hard to figure out. Hashirama was Hokage when Madara and him fought, this was before he gave out the Bijuus because Madara had Kurama at the time and giving all Bijuus to other villages and leaving none for Konoha isn't something Tobirama would except, they gave Bijuus aways/or sold them to balance the power among villages so that had to have take place after Konoha had Kurama as their Bijuu.
Hashirama has SM+ Bijuus 2-9 and Tobirama who made edo Tensei to summon ninjas of their era who as we seen are far stronger than the majority of ninjas currently. Tobirama fatally wounded Izuna with his sword, who's to say he didn't have Izuna, who is equl to Madara (MS). Tobirama created Edo tensei which requires sacrifice yet I see some people saying Tobirama wouldn't sacrifice other lives when he already did creating and using edo tensei in the past.
Juubito's weakness is Senjutsu which Hashirama has and Hashirama wasn't at full power when he said Juubito was stronger than him so it's still wouldn't be an easy fight for Juubito, especially not when Tobirama can mark Hashirama and FTG him out of harm way without touching him as he shown to do using Minato as a medium to FTG ppl who were linked to Minato/Naruto's chakra. Shadow clones can mark the area or he can use water jutsu to fill the area then since the water jutsu is made from his chakra, FTG wherever his chakra is. I don't see another currently shown who can beat this tag team. Edo Hashirama who power was split among clones beat Edo Madara, what would a fully power Hashirama with Bijuus 2-9 do to him?
The Sage, his sons and maybe his mom in my opinion. Maybe Naruto and/or Sasuke in the future since their as strong as they are at 16 (Sasuke)/17 (Naruto) and prime power is usually above 30 years and close to 40 years old.
