SQL Server 2019

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CREATE TABLE #transaction (BankAccountNumber varchar(30), OutboundTransactionId int)
INSERT INTO #transaction (BankAccountNumber, OutboundTransactionId) VALUES
('8002950781',      32078),
('8002950781',      32077),
('8002950781',      32076),
('016200270000486', 32075),
('121054658698',    32074),
('035200146349621', 32073),
('200300019256',    32072),
('200300019256',    32071),
('200300019256',    32070),
('200300019256',    31088),
('018021030517',    31087),
('102957612131',    31086),
('100336018793',    31085),
('100336018793',    31084),
('042033430297001', 31083),
('042033430297001', 31082),
('100336018793',    31081),
('8004062604',      31080),
('102957612131',    31079),
('042033430297001', 31078),
('121054658698',    31077),
('111353490614',    31076),
('121054658698',    31075),
('82455039',        31074),
('110854031395',    31073);

25 rows affected

-- OP's original (tweaked to fit data)

WITH Recent_BankAccountNumber_CTE (BankAccountNumber, TransactionId) AS (
                 SELECT TOP 25 BankAccountNumber, OutboundTransactionId AS TransactionId
                 FROM  #transaction
                 --WHERE CustomerId = 1234
                 ORDER BY TransactionId desc)


SELECT DISTINCT TOP 10 (BankAccountNumber) FROM Recent_BankAccountNumber_CTE;


BankAccountNumber


016200270000486

018021030517

035200146349621

042033430297001

100336018793

102957612131

110854031395

111353490614

121054658698

200300019256


-- Answer

WITH Recent_BankAccountNumber_CTE (BankAccountNumber, TransactionId) AS (
                 SELECT TOP 25 BankAccountNumber, OutboundTransactionId AS TransactionId
                 FROM  #transaction
                 --WHERE CustomerId = 1234
                 ORDER BY OutboundTransactionId desc)
SELECT TOP 10 BankAccountNumber
FROM Recent_BankAccountNumber_CTE 
GROUP BY BankAccountNumber
Order By MAX(TransactionId) DESC;


BankAccountNumber


8002950781

016200270000486

121054658698

035200146349621

200300019256

018021030517

102957612131

100336018793

042033430297001

8004062604