A four letter word beginning with C and ending with X is crux.
a four letter word beginning with X is xebec (a small historical three masted sailing ship with square sails.
There is no synonym for awesome beginning with the letter x.
Coxa
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Xenophobic
Exit, X-ray
x-ray
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Five letter words starting with C and ending with X are calyx and codex.
Xiv, xed, xii.
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