Found 20 stronger alternatives to upgrade your writing.
General negative appearance
Nuance: Unappealing
Simple/clunky.
Boring
That car is ugly.
Better
That car is bad-looking.
Disordered / dirty
Nuance: Disordered
Specific to clutter.
Boring
The room is ugly.
Better
The room is messy.
Not beautiful (polite)
Nuance: Simple/Boring
Polite way to say "not pretty."
Boring
It was an ugly dress.
Better
It was a plain dress.
Frightening appearance
Nuance: Frightening
Fear-based ugliness.
Boring
The mask is ugly.
Better
The mask is scary.
Filthy appearance
Nuance: Filthy
Specific to cleanliness.
Boring
The street was ugly.
Better
The street was dirty.
Not pleasing to look at
Nuance: Not nice
Polite/formal criticism.
Boring
The building is ugly.
Better
The building is unattractive.
Very ugly
Nuance: Revolting
Strong reaction.
Boring
That couch is ugly.
Better
That couch is hideous.
Not nice to see/experience
Nuance: Disturbing
Formal/gentle.
Boring
It was an ugly sight.
Better
It was an unpleasant sight.
Visual sore (formal)
Nuance: Messy to look at
Formal word for visual mess.
Boring
The trash pile is ugly.
Better
The trash pile is unsightly.
Not pretty (people)
Nuance: Plain
Old-fashioned/polite description.
Boring
She was an ugly woman.
Better
She was a homely woman.
Disgusting / dangerous
Nuance: Gross
Physical/visceral.
Boring
That is an ugly cut.
Better
That is a nasty cut.
Disgusting (informal)
Nuance: Disgusting
Strong reaction.
Boring
That bug is ugly.
Better
That bug is gross.
Causes disgust
Nuance: Sickening
Strong physical rejection.
Boring
The smell was ugly.
Better
The smell was repulsive.
Distorted / weird
Nuance: Distorted
Twisted/unnatural shape.
Boring
The statue was ugly.
Better
The statue was grotesque.
Huge and ugly
Nuance: Scary/Huge
Size + ugliness.
Boring
An ugly building blocked the sun.
Better
A monstrous building blocked the sun.
Morally or visually disgusting
Nuance: Disgusting
Strong hatred.
Boring
What an ugly color.
Better
What a vile color.
Extremely disgusting
Nuance: Sickening
Makes you want to vomit.
Boring
The food looked ugly.
Better
The food looked revolting.
Shockingly ugly (death-like)
Nuance: Shocking
Horror/shock.
Boring
He had an ugly wound.
Better
He had a ghastly wound.
Noun for ugly thing
Nuance: Annoying view
Specific noun for ugly landmark.
Boring
That building is ugly.
Better
That building is an eyesore.
Badly formed
Nuance: Deformed
Specific to shape.
Boring
The fruit was ugly.
Better
The fruit was misshapen.