Connie thought Vincent had her father's strength, whatever that meant.
I think you need to put it in context. SHe says he is the only one left with her father's strength. That could mean everyone else was so hopeless that he is the only one who has some degree of her father's toughes. But no way could Vincent hold a candle to Vito.
"Io sono stanco, sono imbigliato, and I wan't everyone here to know, there ain't gonna be no trouble from me..Don Corleone..Cicc' a port!"
