The term "leftist" is too broad and "death penalty" too loosely defined.
Auth-leftists definitely support the death penalty, as in a powerful state should have authority to kill.
Anarchists don't think there should be a state therefore there is no body authorized to kill. If someone must die, it would be at the hands of an individual or an ad-hoc grouping and be called "self-defense".
Thinking things can change without the 0.1% being killed at all is a liberal idea.