A word that starts with S and ends with X is sphinx.
"Rex" is a word that starts with r and ends with x.
reflex
reflux
rituals
No, there is no word in the English language that starts and ends with the letter "x."
X-ray
X-ray
Zanex
xenophobic
ox onyx
xerox
manx
PARADOX
Xerox, Xanax
xyst