Compare Strings ignoring accents in SQL
Specifying a Case-Insensitive or Accent-Insensitive Collation


  Append _AI to an Oracle Database collation name for an
  accent-insensitive and case-insensitive collation.


So I could set, for example:

alter session set nls_sort=hungarian_ai;


But this above will affect only sorts and not the comparisons. You can set comparions to use the sort settings:

NLS_COMP


  LINGUISTIC
  
  Comparisons for all SQL operations in the WHERE clause and in PL/SQL
  blocks should use the linguistic sort specified in the NLS_SORT
  parameter. To improve the performance, you can also define a
  linguistic index on the column for which you want linguistic
  comparisons.


alter session set nls_comp=linguistic;


With both of the above set:

SQL&gt; select 'equals' as result from dual where 'ÁbCdEf' = 'aBcDéF';

RESULT
------
equals