killer

(adjective) difficult

Example Sentence:

Teacher, this homework is so killer. Can’t you make it a bit more easy?

This is a killer assignment.

Mark was scared to go skiing down the hill, because it looked killer.

Similar idioms:

1. killer-2
2. tricky
3. level-headed
4. borderline
5. over the hill
6. show up
7. a hill of beans