How to add character to the end of the output lines by not adding to the last line?

Posting my comments as a separate answer, subquery will order the numbers and outer query will append comma based on rownum and return result in desc order

select GLOBE_MATERIAL_ID_LIST || case when rownum > 1 then ',' else '' end as GLOBE_MATERIAL_ID_LISTfrom (    SELECT DISTINCT CHR(39) || ltrim(MATNR,0) || CHR(39) AS GLOBE_MATERIAL_ID_LIST    FROM PR1_SOAINFRA.WLI_NESOA2_REPORTING_ARCHIVE,          XMLTABLE( '/_-GLB_-OGTX_DESADV01_CUST_ASN/IDOC/E1EDK08/E1EDP07/E1EDP09'                PASSING XMLTYPE(data_value,871)                COLUMNS                MATNR varchar2(2000) path 'MATNR'              )     WHERE ERRORCODE IS NOT NULL AND BUSINESSID = '0000000382153210-E9APRR3103'    order by GLOBE_MATERIAL_ID_LIST) e order by GLOBE_MATERIAL_ID_LIST DESC

SQL Fiddle

Oracle 11g R2 Schema Setup:

create table nums(  id number(10));insert into nums values ('12352682');insert into nums values ('12351436');insert into nums values ('12351434');insert into nums values ('12350683');

Query:

select num || case when rownum > 1 then ',' else '' end as numfrom (select chr(39) || id  || chr(39) as numfrom nums order by num) e order by num desc

Results:

|         NUM ||-------------|| '12352682', || '12351436', || '12351434', || '12350683'  |

It's easy to prepend a comma to every line but the first one...

select distinct case when rownum > 1 then ',' end ||       globe_material_id_listfrom (    SELECT DISTINCT CHR(39) || ltrim(MATNR,0) || CHR(39) AS GLOBE_MATERIAL_ID_LIST    FROM PR1_SOAINFRA.WLI_NESOA2_REPORTING_ARCHIVE,          XMLTABLE( '/_-GLB_-OGTX_DESADV01_CUST_ASN/IDOC/E1EDK08/E1EDP07/E1EDP09'                    PASSING XMLTYPE(data_value,871)                    COLUMNS                    MATNR varchar2(2000) path 'MATNR'                  )     WHERE ERRORCODE IS NOT NULL AND BUSINESSID = '0000000382153210-E9APRR3103');

This has to be an inline query because of your distinct: you need to generate the set of globe_material_id_list before formatting it.