Assuming that you can't get the issuer to issue a corrected W-2 or 1099 (or even admit that there is a problem), what you can do is enter both forms into TurboTax (which the IRS will expect, because they have copies of both), then in Wages & Income->Less Common Income->Miscellaneous Income, 1099-A, 1099-C->Other reportable income enter "Adjustment for duplicate income" and the negative of the amount on either the W-2 or 1099.
This will appear on Line 8 of Schedule 1 (1040) and reduce your overall income to the correct amount.
Make a note of why you did this, in case someone ever asks. To work around an error by the issuer is a perfectly valid reason.
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