GER reverting blood to Diavolo (alongside everything else) Gold Experience Requiem's ultimate ability is to revert actions and willpower back to the state of "zero", completely nullifying them and preventing them from becoming "real".

Is Ger the strongest?

So ger is considered the strongest canon stand.as he is called that because of how araki wrote him.so I am going to go indept on ger and it's very very few weaknesses. So let's start with the small fish.

Can Goku beat Ger?

Again no matter what attack Goku did, or Beerus, or Jiren, they would be nullified to zero. Thus leading GER being able to hit Goku giving him infinite deaths.