The antonyms for the phrase "running alongside" include "opposing," "conflicting," "diverging," "separating," and "detaching." When two things are opposing, they are moving in opposite directions, and there is no way for them to run alongside each other. Conflict arises when two things cannot coexist or move in the same direction. When two things are diverging, they are moving away from each other, while when things are separating or detaching, they are moving in different directions, which is the opposite of running alongside. The antonyms for "running alongside" are helpful in describing situations where two things cannot exist, move, or function in the same or similar manner.