Learn English – What’s the opposite of “no-show”

Looking strictly at the Latin roots of concatenate:

concatenare, from Latin com- + catenare, to chain [MW]

com- is the Latin prefix meaning "together, with."

dis- is the Latin prefix meaning "apart."

(de- means "down or away from," so you can make the case for that as well.)

So: discatenate, or decatenate.

Edit: As I (and FF) noted in a comment, decatenate is used in biology/biochemistry to describe the unlinking of a chain of chemical elements.

The term "offboarding" refers to "Removing a user from an identity management system or downgrading the user's privileges." according to the Free Dictionary. I looked up the term on other websites, and they all concur. New York University even has an article titled "Offboarding Employees" where they discuss what to do when an employee leaves the company.

I hope this answers your question.