How to say "the criminal underworld" in Russian?

What's a general term for "the criminal underworld"?

Also, how would you say in russian "so for our homework last night you wanted us to...?"

криминал, криминальный мир, подпольщина

for the sentense you need more context
here is the literal translation
so for our homework last night you wanted us to.
Так для нашей домашней работы вчера вечером ты хотел, чтобы мы...

"the criminal underworld" - криминальный мир. It is persistent sentence.

"so for our homework last night you wanted us to...?" - "Таким образом, в качестве домашней работы прошлым вечером Вы/ты хотели/хотел, чтобы мы".

I'd vote for "преступный мир". To my mind that's far more frequent than any of the above proposed variants.

Soon it will be one year since OP visited this place last time.