Hash up refers to the act of making a mess out of something, or failing to do it properly. The antonyms for hash up are create, construct, accomplish, execute, and succeed. The word create means to bring something new into existence that has its own unique identity. Construct refers to building something with skill and care, while accomplish is completing something successfully. Execute means to carry out a plan or task with precision or skill, and succeed means to achieve a goal or accomplish an objective. These antonyms all convey a sense of proficiency, proficiency, and success, which are the opposite of the meaning of hash up.