The word "under-going" means experiencing or undergoing something. Antonyms for "under-going" would include terms such as not experiencing, avoiding, sidestepping, evading, bypassing, and ignoring. For example, if someone avoids a challenge or obstacle, they are not undergoing it. If someone sidesteps a situation, they are not undergoing it. If someone ignores a difficulty, they are also not undergoing it. These antonyms highlight the opposite of "under-going" and suggest attempts to escape or avoid challenging situations rather than facing them head-on.