I am using Oracle 12c and also SQL developer 18.2.
Try to figure out if a user can kill process/sessions.
In tools menu there is a monitor sessions.
I login sql developer by using a user (for example user sales) that has many priviliges but not a dba role.
I find I can kill my own process that has a user name sales if I want.
But I did a query using SELECT * FROM DBA_SYS_PRIVS where grantee='sales';
I found it has NO values on Alter System privilege.
So why I don't have alter system privilege but still can kill my own sessions from SQL developer- Monitor sessions.