Purely as a matter of opinion, the way to think about this is not as an advantage for an individual, but for as a gene pool.
Mostly a human gene pool's survival and prosperity is best served by community co-operation, mutual support and self sacrifice for the good of loved ones and other community members. Sometimes though, the group as a whole has had it and the route to the survival of any of the gene pool is for one or a few to sacrifice the rest and make an all-out bid for personal survival. E.g. a terrible winter in which there is insufficient food and everyone is starving to death.
Another situation where psychopathy could be useful is warfare. Sometimes having a cold blooded killer with no remorse on your side isn't such a bad thing.
Ultimately, it's a matter of variety. You never know what challenges your community is going to face, and what range of behaviors are going to be optimal. Having a full range of behavior types available in your community gives it flexibility in it's response, especially to to existential challenges.
Mostly a human gene pool's survival and prosperity is best served by community co-operation, mutual support and self sacrifice for the good of loved ones and other community members. Sometimes though, the group as a whole has had it and the route to the survival of any of the gene pool is for one or a few to sacrifice the rest and make an all-out bid for personal survival. E.g. a terrible winter in which there is insufficient food and everyone is starving to death.
Another situation where psychopathy could be useful is warfare. Sometimes having a cold blooded killer with no remorse on your side isn't such a bad thing.
Ultimately, it's a matter of variety. You never know what challenges your community is going to face, and what range of behaviors are going to be optimal. Having a full range of behavior types available in your community gives it flexibility in it's response, especially to to existential challenges.