SQL Server 2017

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--load test data
declare @table table (c1 int, c2 int, c3 int)
insert into @table
values
(1,1,1)
,(1,1,1)
,(2,3,2)
,(4,2,4)
,(5,4,6)
,(7,5,8)
,(9,7,11)
,(11,9,13)
,(14,16,15)

--get our unique values in a cte to pivot later
;with cte as(
select 
    --here we add a RN so that we can use pivot without losing values
    r = row_number() over (partition by Col order by (select 1))
    ,i.*
from
    (
    --for each column, we get the unique values where they don't exist in the other two columns
    --we union them together, but give them 1 /2 / 3 column identifier
    select
        1 as Col, c1.c1 as val
    from
        (select distinct t1.c1 from @table t1
         where  not exists (select 1 from @table t2 where t2.c2 = t1.c1)
            and not exists (select 1 from @table t3 where t3.c3 = t1.c1)) c1
    union
    select 
        2 as col, c2.c2
    from
        (select distinct t1.c2 from @table t1
         where  not exists (select 1 from @table t2 where t2.c1 = t1.c2)
            and not exists (select 1 from @table t3 where t3.c3 = t1.c2)) c2 
    union
    select
        3 as col, c3.c3
    from
        (select distinct t1.c3 from @table t1
         where  not exists (select 1 from @table t2 where t2.c1 = t1.c3)
            and not exists (select 1 from @table t3 where t3.c2 = t1.c3)) c3
    ) i
)

--simple pivot
select
    [1], [2], [3]
from cte 
pivot
(max(Val) for Col in ([1],[2],[3]))
p

1	2	3
14	3	6
null	16	8
null	null	13
null	null	15