How does one backout the Child and Other Dependent Tax Credit.

Remove the dependent that is populating the credit you do not want.  

What are you trying to do and what are your circumstances? As Critter-3 said, in most cases you just don't enter the dependent in TurboTax. 

But there are times (divorced parents)  when you need to list a non-dependent child, for tax benefits that the custodial parent gets, even when the non custodial parent is claiming the Child Tax Credit or  the Other Dependent Tax Credit.  In that case, the TurboTax interview asks you if you are letting the other parent claim the child.

A common error is when unmarried parents live together,  If you and the other parent live together, only one of you can claim the child for any tax benefit. The TurboTax interview is confusing (it's designed for divorced parents, who are allowed to split the child). The second parent should not enter the child, at all.

  If you and the other parent are not married, and live together, either one of you (but not both) may claim the child. You may decide between you which one will claim the child. Only if you can’t agree, do the IRS tie breaker rules apply, to see who has first choice. It may be worthwhile to prepare trial returns, both ways,  to see which way the family comes out best. This tool may be useful:https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1.