Unlock SIEBEL Object Forcefully

here are two ways to do this:

If you know the users password, login to the server using that login and unlock. But most of the times the passwords would have been changed. In this case request for a password change and then login using this new password unlock it. If this is not possible and some reason you are not able to login, then use the second method.
This is a sure shot method of unlocking. Login to the Siebel server database with table owner siebel. Unlock the object using a SQL update on the base table as per object.

Example:

UNLOCK REPOSITORY OBJECTS

VIEW
UPDATE SIEBEL.S_VIEW T1 SET T1.OBJ_LOCKED_FLG = 'N', T1.OBJ_LOCKED_DATE = NULL, T1.OBJ_LOCKED_BY = NULL, T1.OBJ_LOCKED_LANG = NULL
WHERE T1.ROW_ID = ‘X-XXXX-XXXXX’;
COMMIT;

TABLE
UPDATE SIEBEL.S_TABLE TBL SET TBL.OBJ_LOCKED_FLG = 'N', TBL.OBJ_LOCKED_DATE = NULL, TBL.OBJ_LOCKED_BY = NULL, TBL.OBJ_LOCKED_LANG = NULL
WHERE TBL.NAME = ‘S_APPLICATION’
AND TBL.ROW_ID = 'X-XXXX-XXXXX';
COMMIT;

BUSCOMP
UPDATE SIEBEL.S_BUSCOMP BC SET BC.OBJ_LOCKED_FLG = 'N', BC.OBJ_LOCKED_DATE = NULL, BC.OBJ_LOCKED_BY = NULL, BC.OBJ_LOCKED_LANG = NULL
WHERE BC.ROW_ID = ‘X-XXXX-XXXX’;
COMMIT;

BUSSERVICE
UPDATE SIEBEL.S_SERVICE SERV SET SERV.OBJ_LOCKED_FLG = 'N', SERV.OBJ_LOCKED_DATE = NULL, SERV.OBJ_LOCKED_BY = NULL, SERV.OBJ_LOCKED_LANG = NULL
WHERE SERV.ROW_ID = 'X-XXXX-XXXX';
COMMIT;

APPLET
UPDATE SIEBEL.S_APPLET APPL SET APPL.OBJ_LOCKED_FLG = 'N', APPL.OBJ_LOCKED_DATE = NULL, APPL.OBJ_LOCKED_BY = NULL, APPL.OBJ_LOCKED_LANG = NULL
WHERE APPL.ROW_ID = 'X-XXX-XXXX';
COMMIT;

PROJECT
UPDATE SIEBEL.S_PROJECT AS PROJ SET PROJ.LOCKED_FLG = 'N', PROJ.LOCKED_DATE = NULL
WHERE PROJ.NAME = 'Account Hierarchy';
COMMIT;

Note:-
How to find out the row id of any object?
Go to Siebel tools
Select object(Applet/BC/View) -> Help -> About Record -> Details
Row# will give the Row Id details.

Seek the help of Siebel Admin if you need.

I have tried this and it has worked. Though this is very simple, do this very carefully because the changes that the user had made will not be checked in. So be sure of what you are doing.