It was a really good chapter, more Ryohei, damn it.
And for some reason, the first person who came to mind when he mentioned the "person with the biggest grudge to Vongola" was Vongola Primo
Well then it would no make no sense that they hate Primo. If he was the source somehow informing them about the future battles with Millefiore (I guess something like can be done xD), then they would be thanking him . I guess it will be someone from Vongola, but I think it's not Primo.