During conversations with native German speakers, I have heard the word "krass" used in different contexts. But I still don't know how to translate it.
"krass" is actually not such a new word as it's modern slang usage suggests. It is a loanword from Latin "crassus" and as such shares the same etymology as the English "gross" does.
In general usage "krass" is used for extremes in either a positive or mostly a negative connotation:
From the 18. Century krass was also used by students, apparently first in the idiom
The Grimms wrote in their dictionary:
Only in recent years "krass" is also used in German youth slang with several meanings that have already been pointed out.
An appropriate translation can not be done without a context because of the so many different meanings "krass" can have.
"Krass" as a slang term can mean many different things from "cool" over "that's odd" to "what a pity". It depends on the situation. Colloquially it's an all purpose adjective, mainly used by young people. For emphasizing you can use it together with "voll".
These are not the best examples, but I hope you get the idea.
According to German wiktionary: (translations below each line)