For sheer size and ugliness:
* Monstrous: Implies something large, deformed, and frightening.
* Gargantuan: Emphasizes the immense size, often with a negative connotation.
* Colossal: Similar to gargantuan, but can sometimes imply a sense of grandeur, even if it's ugly.
* Hulking: Suggests a large, clumsy, and unattractive physique.
* Grotesque: Highlights the bizarre and unpleasant aspects of the object.
For emphasizing ugliness:
* Hideous: Describes something extremely ugly and repulsive.
* Abhorrent: Expresses strong dislike or disgust.
* Repulsive: Something that causes revulsion or aversion.
* Horrifying: Evokes a sense of fear and dread.
For a more poetic or descriptive approach:
* Vast and unlovely: Combines the size with the negative aesthetic.
* Immense and grotesque: Emphasizes both the largeness and the ugliness.
* A colossal eyesore: Highlights the visual impact of the ugliness.
The best choice will depend on the context and what you want to emphasize.