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.
smoother is comparative of word smooth.
A comparative for the word ineffectual is more ineffectual.
comparative
The visitor was kindly welcomed.
Dayf (visitor) Dyoof (visitors)
The rhyming word for superior visitor is competitor.
Yes, the word visitor has three syllables. Vis-i-tor.
Sharper is the comparative form of the word sharp.
There are three syllables in the word "visitor."