single-minded: having only one purpose, goal, or interest; focused on one thing; having one driving purpose or resolve. First known use 1836.
Synonyms: bent (on or upon), bound, decisive, do-or-die, firm, hell-bent (on or upon), intent, purposeful, resolute, resolved, set. Antonyms: faltering, hesitant, indecisive, irresolute, undetermined, unresolved, vacillating, wavering, weak-kneed.
In American thinking to be single-minded is always positive. It means to be wholly focused.