If a Google Sheets spreadsheet has rows with duplicates, there’s a way to highlight where the duplicates are located, and then manually delete them: From LifeWire:
Open the spreadsheet you want to analyze in Google Sheets.
Highlight the column you want to search through.
Click Format > Conditional Formatting. The Conditional Formatting menu opens on the right.
Confirm the cell range is what you selected in Step 2.
In the Format cells if… drop-down, select Custom formula is. A new field appears below it.
Enter the following formula in the new field, adjusting the letters for the column range you selected:
In the Formatting style section, choose a fill color for the duplicate cells. In this example, we’ve chosen red. Then click Done.