The Messenger of Allah [SAW] said: "The first matter concerning which scores will be settled among the people on the Day of Resurrection will be bloodshed." (Using translation from Nasāʾī 3993)
قَالَ عَبْدُ اللهِ «أَوَّلُ مَا يُقْضَى بَيْنَ النَّاسِ يَوْمَ الْقِيَامَةِ فِي الدِّمَاءِ»