What is the country that has the most perpetrators?
select country, count(*) from perpetrator group by country order by count(*) desc limit 1;
Which ones have more more than 1 perpetrator?
select country, count(*) from perpetrator group by country having count(*) <= 1;
How about those with at least two perpetrators?
select country, count(*) from perpetrator group by country having count(*) >= 2;