While "reaching the zenith" suggests the pinnacle of achievement, there are many antonyms that describe failure, struggle or falling short. Some of these antonyms include "hitting rock bottom," "hitting the floor," "reaching the nadir," "hitting a low point," "hitting a dead end," "bottoming out," "plateauing," "losing altitude," "falling short," "fizzling out," "stagnating," and "coming up short." These words illustrate the opposite of reaching the pinnacle and indicate a lack of progress, achievement, or success. However, it is important to remember that failure is not a permanent state, and with hard work and perseverance, one can always strive to reach the zenith again.