Should one help a group of people who hurt him/her in the past?

A person was born into a group of people (clan, society, whatever have you). Not only did that group not help him/her, they did nothing when he/she was in pain and clearly suffering from certain conditions that were caused by that group.

They choose to ignore and pretty much forgot and abandon this person and continue to live their lives.

Now this group is in big trouble and the only person that can help them is the one they abused. But the group is not aware of this, he/she is the only one who knows.

Should this person forget the past, sacrifice himself/herself and spend the rest of his/her life fixing the issues and problems that he/she inherited, not only from the current generation, but past generations as well.

Or live out the rest of his/her life and try to enjoy whatever time he/she has left.

[If this question makes no sense, please ask question and I will explain the parts that don’t make sense] thanks