Have you try Row_Number function? Here is an example using CTE and Row_Number functions.
DECLARE @temp TABLE ([KEY] INT, WO INT, Parts INT, Name VARCHAR(10), Panels INT)
INSERT INTO @temp
SELECT 77, 11, 1, 'aa' , 3
UNION
SELECT 77, 11, 2, 'aa' , 4
UNION
SELECT 81, 12, 2, 'bb' , 5
UNION
SELECT 82, 9, 3, 'cc' ,6
SELECT * FROM @temp
;WITH temp AS (
SELECT ROW_NUMBER() OVER (PARTITION BY [Key]
ORDER BY [Key] DESC
) AS myrownum
,*
from @temp )
SELECT [Key], WO 'WO#', Parts, Name, Panels FROM temp WHERE myrownum = 1
Output:
Key WO# Parts Name Panels
77 11 1 aa 3
81 12 2 bb 5
82 9 3 cc 6