Myself and a lot of other people don’t believe in death sentence no matter the severity of the crime.
https://en.wikipedia.org/wiki/Capital_punishment_by_country
The two main reasons why I don’t support a death sentence in any case are:
1. People sometimes get sentenced for crimes they did not commit. By at least letting them live in prison rather than killing them we give them a chance to fight the sentence.
2. The law is not objectively “correct” because there is no such thing as a single “true” morality. Multiple moral stances exist, and we should be somewhat tolerant of that.
Amnesty International has some more arguments against death penalty as well. https://www.amnesty.org/en/what-we-do/death-penalty/
Finally I believe that the justice system should to the greatest extent possible exist to prevent crime and reform criminals so that they can be productive members of society, not primarily exist to punish criminals.
In my country — Norway — this is reflected in how the police handle confrontational situations. The Norwegian police force always tries to deescalate, whereas in the US the police are very aggressive in a lot of situations that should not call for that sort of reaction.
There are very many people that do bad things not because they are fundamentally bad people but because of their circumstances. Everyone deserves a chance.
Some people cannot be helped and need to remain locked up because they pose a threat to the rest of society, but that should be what we do when we see that we cannot reform them, not how we treat everyone who breaks the current set of laws.