What should the law be for rapist (valid proof) and murderers?

I watched a video of a prison documentary in El Salvador. And I feel sick to my stomach looking at the gangmembers behind the bars and their tattoos proudly displayed of the crimes and suffering they caused other innocent people. Through the video and watching the interview where the leader asks for a second chance to show he has changed after experiencing prison life. This made me sick to my stomach. That they would dare ask for a second chance, when they mercilessly ended lives and caused suffering to hundreds or more. Prison life was merciful in my perspective for these monsters. Acknowledging that there are WORSE criminals like Donald Trump and Jeffrey Eptsein and ect, out there free. But I feel that the law needs to ensure they are held accountable for huge offenses with backed up proof like this. There are no second chances to those who commit crimes, with proof, like murder and rape or any sort of violence on others with the intention to harm others. No second chance, because there is no bringing back the dead and restoring a person livelihood 100% after facing acts of violence. The criminal with these offenses, should suffer their whole lives or die, for the wrongs they committed, a consequence for their actions.