The word undermining means to weaken, damage or subvert something, so it stands to reason that its antonyms would be words that relate to building up or strengthening. Some antonyms for undermining could include reinforcing, supporting or strengthening. Other possibilities might include uplifting, upholding, buttressing or fortifying. These words all imply some kind of positive action or intervention, a contrast to the harmful or destructive forces implied by undermining. By using antonyms to undermine, we can create a positive and constructive approach to problem-solving, focusing on building something up rather than tearing it down.