Is "hero" a subjective qualification?

Can someone who, through negligence, or direct involvement, has multiple deaths to its name, do anything to make up for said wrongdoings, and become (or be seen as) a hero?
And who is to judge whether that person is then a hero?
Can my asshole be your hero (or vice versa)?
Replace asshole for something else, according to your liking…
Could Pol Pot have done something very humane, after his policies that killed many of his people, and be seen as a good guy, in hindsight?
Hitler? Genghis Khan? Ivan the Terrible?
I’m asking this after this morning I read and watched Mike Pompeo’s message (from Mr. Trump) directed at North Korea, and its leader, Kim Jong Un.
“Secretary of State Mike Pompeo said Sunday that if North Korea replicates the path Vietnam has taken with its partnership with the U.S., Kim Jong Un would get a “miracle” and be seen as a “hero of the Korean people.””
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Will the Korean people, potentially, agree, would you think?