You can find them using CTE.

with cte_Test

as (

select [DropdownID]

, [OrderSequence]

, COUNT(*) CountDuplicated

, MIN([Description]) FirstDescription

from TestData

group by [DropdownID]

, [OrderSequence]

having COUNT(*) > 1

)

-- select * from cte_Test

select td.*

from TestData td

inner join cte_Test ct on ct.DropdownID = td.DropdownID and ct.OrderSequence = td.OrderSequence

With this you can define wich records will be deleted.