This world is not based on ‘fair justice’. People get hurt, pained, or killed without being at fault. When you complain about these injustices, you should remember that everything that happens is in the knowledge of God and He will compensate you, in this life or hereafter. Therefore, one needs to keep faith in Him.
This life is not supposed to be all comfy and fair. It is a ‘test’ and tests and examinations are supposed to be difficult. The more you prepare and suffer for a test, the better results you can expect, eventually.