He said it right to Tobirama's face.
Hiruzen > Danzo
Hiruzen > Ei
Hiruzen > Gaara Sr.
Hiruzen > Minato
Hiruzen > Onoki
Hiruzen > Orochimaru
Hiruzen > Tobirama
Hiruzen > Yagura
Well with that single squirt gun and unimpressive Suiton feats, I can tell Prime Hiruzen would have been better, stronger, and more skilled. People overhype Tobirama for nothing, when this guy's feats are lackluster. He was killed by Bounty Hunters, for Godsake, when he has FTG at his disposal. That tells one something.
Flying Thunder God
Four Red Yang Formation
Impure World Resurrection
Mutually Multiplying Explosive Tags
Revolving Flying Thunder God
Sensing
Shadow Clone
Water Dragon Missile
Water Encampment Wall
Water Severing Wave
Was the fastest shinobi of his era, and was surprised that Minato was faster than him.
Solo'd Izuna, and Hashirama feared Tobirama would kill Madara.
Lifted his finger and Sasuke stopped being so cocky.
The group of bounty hunters were obviously elite shinobi, likely led by Kinkaku and Ginkaku (especially since they know Tobirama was dead). They themselves attacked Tobirama and the 2nd Raikage during a peace treaty, and Tobirama was the only one said to have survived (particularly since they were aware of who the 3rd Raikage was). KinGin + 18 other elite bounty hunters threatened to take out Tobirama's whole group.