Try this simple method:

First get the asci value of that character like the below ex:

SQL> SELECT DUMP(JOB) FROM EMP WHERE EMPNO = 7902;

DUMP(JOB)
--------------------------------------------------------------
Typ=1 Len=7: 65,78,65,76,89,83,84

In the above ex. the job column is having the value ANALYST.
If you wanted to remove the T character which is in the last
then

SQL> SELECT REPLACE(JOB,CHR(84)) FROM EMP WHERE EMPNO=7902;

REPLACE(J
---------
ANALYS

But make sure that the character you remove is not present in any other place. i.e
if the job is having value as ANALTYST then it will remove both the "T".