There's stories I've heard where people got rejected by their parents, abused, raped and then they end up not wanting to live because that trauma stays forever or for a long time and sometimes they keep struggling in life. I want to know why some people have better lives than others and why some people were just destined to suffer because it doesn't seem fair. A lot of those people who suffered end up committing suicide

Each person has his/her unique trial in this world. Sometimes such people suffer because God is trying them and their families who abused them. God will infinitely compensate the one who suffered and He will punish those who abused him. Why did God allow Imam Hussain (a) to suffer in Karbala? To elevate his status and to try his enemies and punish them.
Now the one who is abused should never commit suicide. They should be patient and Allah will compensate them.