Query:

 select blocking_session,blocked_session,script from 
( select distinct 
s1.username || '@' || s1.machine || ' ( INST=' || s1.inst_id || ' SID=' || s1.sid || ' ET=' || s1.last_call_et || 'sn. STATUS=' || s1.status || ' EVENT=' || s1.event || ' ACTION= ' || s1.action || ' PROGRAM=' || s1.program || ' MODULE=' || s1.module || ')' blocking_session,
s2.username || '@' || s2.machine || ' ( INST=' || s2.inst_id || ' SID=' || s2.sid || ' ET=' || s2.last_call_et || 'sn. STATUS=' || s2.status || ' EVENT=' || s2.event || ' ACTION= ' || s2.action || ' PROGRAM=' || s2.program || ' MODULE=' || s2.module || ')' blocked_session,
decode(s1.type,'USER','alter system kill session ''' || s1.sid || ',' || s1.serial# || ',@' || s1.inst_id || ''' immediate;' ,null)
script ,
count(*) over (partition by s1.inst_id,s1.sid) blocked_cnt
from gv$lock l1, gv$session s1, gv$lock l2, gv$session s2
where s1.sid=l1.sid and s2.sid=l2.sid
and s1.inst_id=l1.inst_id and s2.inst_id=l2.inst_id
and l1.block > 0 and l2.request > 0
and l1.id1 = l2.id1 and l1.id2 = l2.id2 )
order by blocked_cnt desc;