def get_unique_rows(df, columns, sort_by):
    """De-dupe a Pandas DataFrame and return unique rows.

    :param df: Pandas DataFrame.
    :param columns: List of columns to return.
    :param sort_by: Column to sort by.
    :return: Pandas DataFrame de-duped to remove duplicate rows.
    """

    df = df[columns]
    df = df.drop_duplicates(subset=None, keep='last', inplace=False)
    df = df.sort_values(sort_by, ascending=False)
    return df