The phrase "almost on one" implies a sense of being alone, or nearly so. Some antonyms for this phrase might include "surrounded," "crowded," or "packed." These words suggest a sense of being completely filled up, with no empty space or room to move around. Other options might include "connected," "related," or "together," which imply a strong sense of community or shared experience. Ultimately, the choice of antonym will depend on the context in which the original phrase was used, as well as the intended meaning and tone.