Sure, some actions are more harmful than others. Killing a person is worse than imprisoning them indefinitely.

But the degree to which it is worse (and whether it is enough to ban the death penalty) seems quite subjective.

Seems to me that you could use an identical line of reasoning to conclude that prison sentences longer than N years should be banned.

Is it a matter of degree? Or is there something fundamentally different about the death penalty that warrants a ban?