"Is that a Fledgling power?" -Ethan
"Not a power, just a perk." -Sarah"
Ethan and Sarah discussing her vampire strength. Blue Moon
Superhuman Strength is the supernatural ability of superior physical strength. Those with superhuman strength are stronger and more physically powerful than any human, regardless of their age, gender, size, weight, or physical fitness. Vampires are known to possess this power. The only other know species known to posses this power are werewolves, who are about as strong as vampires.
Boltz was also incredibly strong, strong enough to overpower two vampires at once, so far he is the only known thing that is stronger than vampires. He also doesn't count, as he was another artifical creation. (Jockenstein)