SELECT regexp_replace('ñaàeéêèioô','[[=n=]]','n' )
FROM dual;

Output:
naàeéêèioô

SELECT translate('ñaàeéêèioô','ñàéêèô','naeeeo') FROM dual;

SQL> SELECT CONVERT('ñaàeéêèioô', 'US7ASCII' ) FROM dual;

CONVERT('ÑAÀEÉÊÈIOÔ','US7ASCII')
----------------------------------------
?aaeeeeioo

select distinct chr(level)
from dual
connect by level <= 256

select translate('Target™','™','TM') from dual


Required Output
===============
TargetTM

SCOTT@orcl_12.1.0.2.0> SET UNDERLINE '='
SCOTT@orcl_12.1.0.2.0> COLUMN "Required Output" FORMAT A15
SCOTT@orcl_12.1.0.2.0> SELECT REPLACE ('Target™', '™', 'TM') AS "Required Output" FROM DUAL;

Required Output
===============
TargetTM

1 row selected.

select replace('Target™',chr(ascii('™')),'TM') from dual