UPDATE t2 SET
	t2.a = CASE WHEN t1.clientcode = 'A' THEN 1 ELSE t2.a END,
	t2.b = CASE WHEN t1.clientcode = 'B' THEN 1 ELSE t2.b END
	--- other columns here
FROM
	Table2 t2
	INNER JOIN Table1 t1 ON
		t1.leadid = t2.leadid
WHERE
	t1.ClientCode IN ('A','B','C','D','E','F','G','H','I','J');

UPDATE t
SET A= SIGN(ACnt),
SET B= SIGN(Bcnt),
SET C= SIGN(Ccnt),
...
FROM Table2 t
INNER JOIN (SELECT leadid,
                   SUM(CASE WHEN ClientCode='A' THEN 1 ELSE 0 END) AS ACnt,
                   SUM(CASE WHEN ClientCode='B' THEN 1 ELSE 0 END) AS BCnt,
                   SUM(CASE WHEN ClientCode='C' THEN 1 ELSE 0 END) AS CCnt,
                   ...
           FROM Table1
           GROUP BY leadid
           )t1
ON t.leadid = t1.leadid