Why did all Kurta Clan get beaten up even though they have the Scarlet Eyes? Kurapika is so powerful with his Scarlet Eye. We already know that all Kurta Clan has the Scarlet Eye.

According to that, why did all the other members of the Kurta Clan get massacred by the Phantom Troupe? 

Couldn't they use the Scarlet Eye to fight back Phantom Troupe? Is there no "hero" in Kurta clan, or in this context, a person that has improved and mastered his Scarlet Eye?
There is an inherent assumption in the question, "IF Kurapika is so powerful with his scarlet eyes...". Yes it is true that when a member of Kurta clan becomes enraged they gain an increase in physical strength, however they lose their rationality and revert to a primal form. We do not know if the "Scarlet Eyes" causing Kurpika to become a specialist is unique to him or the Kurta clan. Your other question regarding the so called "hero" has simply no base or answer at all because the Manga gives no information.

However, you've to understand that the Phantom Troupe themselves are very powerful Nen Users. They can easily go against numerous "physically powerful" people, they can easily kill them. This is what Nen brings to the table and all members of The Phantom Troupe.

Kurapika was able to bridge the gap by utilizing his "Scarlet Eyes". He was able to turn his eyes Scarlet at will. By utilizing the conditions of Limitations and putting his own life at stake he greatly boosted his Nen abilities. He is a skilled Nen User, has high combat prowess, genius level intellect, and enhanced speed, perception and reflexes.

To end, as far as we know Kurapika is strong BECAUSE of his clan massacre and his innate skill and not because of his clan. The Phantom Troupe is an elite group of Nen Users who can take on any other high level fighters. We don't have enough history about Kurta clan to know if there was another "hero" for the clan.