the.com/cull
To choose by killing, or kill by choosing — depends how much you like the verb.
means To selectively remove or reduce a group, often by eliminating the weakest, unwanted, or surplus members.
from From Latin colligere, to gather or collect — the same root as collect. Curiously, a word for gathering became a word for thinning out, as if picking the best inevitably means discarding the rest.
Gentle cousinTo cull also means simply to select or pick.
Wildlife useHerds are culled to manage population and disease.
Spinoff nounA culling can mean any ruthless trimming of numbers.