agent
Shopper is an agent, not a comparative. Many of the words ending in -er are comparative because they are based on a comparison like big, bigger, biggest, fast, faster, fastest. But when the word changes from an action to a person or noun then it is an agent like shopper, editor, creator, etc.
Visitor
"Litter" is a noun and a verb and, as such, does not have a comparative degree.
A comparative for the word ineffectual is more ineffectual.
smoother is comparative of word smooth.
comparative
Dayf (visitor) Dyoof (visitors)
The visitor was kindly welcomed.
Yes, the word visitor has three syllables. Vis-i-tor.
The rhyming word for superior visitor is competitor.
Sharper is the comparative form of the word sharp.
comparative