Return only one row from table with similar values in column that match a criteria
You can use the EXCEPT keyword:

CREATE TABLE #T1(c1 char(1), c2 int)
go

INSERT INTO #T1 Values('A',1)
INSERT INTO #T1 Values('A',2)
INSERT INTO #T1 Values('A',3)
INSERT INTO #T1 Values('A',4)
INSERT INTO #T1 Values('B',1)
INSERT INTO #T1 Values('B',2)
INSERT INTO #T1 Values('C',1)
INSERT INTO #T1 Values('C',3)
INSERT INTO #T1 Values('C',4)
INSERT INTO #T1 Values('D',2)
GO

SELECT c1 FROM  #T1
EXCEPT 
SELECT c1 FROM #t1 WHERE c2 = 3

DROP table #T1