The phrase "most untidied" pertains to something that's extremely disorganized or messy, which can be described using various synonyms. Some of the words that can replace "most untidied" are disheveled, cluttered, chaotic, shambolic, topsy-turvy, unkempt, disorderly, messy, jumbled, and disarranged. Each of these synonyms presents a different facet of messiness, but they all suggest a certain lack of order, cleanliness, or tidiness. Some of these words can also be used to describe situations or environments, not just physical spaces, where there's a lot of confusion or disarray. Whatever term one chooses, the meaning is clear: something most untidied is the opposite of neat, tidy, and organized.