with  
  qwert as (select '123123' as contracts, '123' as contrackind, '1111' as clients from dual
  union all
  select '123124' as contracts, '123' as contrackind, '1111' as clients from dual
  union all
  select '123125' as contracts, '123' as contrackind, '1112' as clients from dual)
  select k.* from (
select q.contracts, q.contrackind, q.clients, row_number() OVER (PARTITION BY q.clients ORDER BY q.clients DESC) AS RN
  from qwert q 
  ) k
  where k.rn= 1