Retch vs. Wretch
Do you confuse these words? "Retch" and "wretch" may sound alike, but their meanings are completely different. Mixing them up could create some unintended humor. I've seen it in action. LOL. 
"Retch" is a verb that refers to vomiting, being on the verge of vomiting, or making the sound and movement of trying to vomit.
Example Sentences:
The stench from the restaurant's dumpster made him retch as he passed by.
My mom and step-dad's over-the-top PDA makes me retch.
The taste of the spoiled milk made him retch involuntarily.
The gruesome crime scene was enough to make even the seasoned detective retch.
"Wretch" is a noun used to describe a miserable, pitiable, or unfortunate person; or a vile, despicable, or contemptible person.
Example Sentences:
The poor wretch huddled in the cold alley, hoping for a kind soul to offer some warmth.
The wretch in the story, abandoned and heartbroken, became a central figure in the unfolding romantic drama.
The conniving wretch betrayed his closest friend for personal gain.
The novel's antagonist, a cunning and deceitful wretch, plotted to ruin the lives of the main characters.
To sum it up, "retch" is related to vomiting, while "wretch" describes a person who is pitiable, miserable, or vile. As you can see, mixing them up would drastically change the meaning of the sentence.