The Base Saiyans. There's loads of evidence for this too.
The Saiyans decide to fight in Base in the 25th Budokai. Piccolo implies Kaioshin is stronger than him in the Budokai, who turns out to be weaker than the Base Saiyans as well.
Base Gohan seems to be a lot stronger than Kibito going by the evidence involving the Zeta Sword, who is implied to be around Kaioshin's level of strength.
There's other instances of Base Saiyan wank in the Boo Saga in general. Gotenks surpassing his Super Saiyan form in his Base Form in the ROSAT, as well as the Saiyans fighting in Base during the 28th Budokai, and Goku is able to fight on par with Oob in Base, who is as strong as Kid Boo was.
Those who believe Piccolo > Base Saiyans tend to only use the evidence we see in the Cell Games, which does point to that being the case, but I would rather apply the Boo Saga's logic to Piccolo's strength because I like to think of it as a retcon instead of just calling it messy writing like those who argue Piccolo > Base Saiyans, even if the Boo Saga does indeed suck. There's more evidence for Base Saiyans > Piccolo than there is Piccolo > Base Saiyans, anyway.