SQL Server 2017

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WITH yourTable AS (
    SELECT 'A' AS Col1 UNION ALL
    SELECT 'B' UNION ALL
    SELECT 'C' UNION ALL
    SELECT 'D' UNION ALL
    SELECT 'E' UNION ALL
    SELECT 'F' UNION ALL
    SELECT 'G' UNION ALL
    SELECT 'H' UNION ALL
    SELECT 'I' UNION ALL
    SELECT 'J' UNION ALL
    SELECT 'K' UNION ALL
    SELECT 'L' UNION ALL
    SELECT 'M' UNION ALL
    SELECT 'N' UNION ALL
    SELECT 'O' UNION ALL
    SELECT 'P' UNION ALL
    SELECT 'Q' UNION ALL
    SELECT 'R' UNION ALL
    SELECT 'S' UNION ALL
    SELECT 'T' UNION ALL
    SELECT 'U' UNION ALL
    SELECT 'V' UNION ALL
    SELECT 'W' UNION ALL
    SELECT 'X' UNION ALL
    SELECT 'Y' UNION ALL
    SELECT 'Z'
),
cte AS (
    SELECT Col1, ROW_NUMBER() OVER (ORDER BY Col1) rn
    FROM yourTable
)

SELECT
    MAX(CASE WHEN (rn-1)/5 = 0 THEN Col1 END) AS col1,
    MAX(CASE WHEN (rn-1)/5 = 1 THEN Col1 END) AS col2,
    MAX(CASE WHEN (rn-1)/5 = 2 THEN Col1 END) AS col3,
    MAX(CASE WHEN (rn-1)/5 = 3 THEN Col1 END) AS col4,
    MAX(CASE WHEN (rn-1)/5 = 4 THEN Col1 END) AS co15
FROM cte
GROUP BY
    (rn-1)%5;

col1	col2	col3	col4	co15
A	F	K	P	U
B	G	L	Q	V
C	H	M	R	W
D	I	N	S	X
E	J	O	T	Y

Warning: Null value is eliminated by an aggregate or other SET operation.