Antonyms for "betters oneself" include "deteriorate," "degrade," "exacerbate," "regress," "worsen," and "weaken." These terms suggest a decline or weakening of one's abilities or qualities, rather than an improvement. While "betters oneself" connotes personal growth and development, these antonyms imply a loss of progress, a setback, or a failure to advance. It's important to recognize that life is not always a linear path towards success and that setbacks are a normal part of the journey. However, it's essential to strive continuously towards self-improvement rather than allowing oneself to stagnate or regress.