The phrase "make serpentine" refers to creating a winding or twisting shape, so antonyms would be words that mean straight or streamlined. Some possible antonyms for "make serpentine" include straighten, unbend, untwist, flatten, and smooth. These words imply a sense of order and efficiency rather than the chaotic, winding nature of things that are serpentine. For some contexts, these antonyms may be more appropriate - for example, if you were designing a sleek, modern building or creating a perfectly manicured garden path, you might opt for a straight, streamlined look rather than a serpentine one.