Antonyms for the word "most stouthearted" would include weak-willed, timid, fearful, faint-hearted, and spineless. These words describe individuals who lack courage, resolution, and bravery when facing challenges or hardships. A weak-willed person tends to falter under pressure, whereas a timid person is easily intimidated and shy. A fearful person is often anxious and uneasy, while someone who is faint-hearted lacks the mental or emotional toughness to withstand adverse situations. Finally, a spineless person is easily swayed, lacks conviction, and is unable to stand up for themselves or their beliefs. All of these contrasting words are the opposite of being stouthearted, which is characterized by courage, dauntlessness, and fortitude.