Your toughest FB HIIT!

Hi!

As a very busy working person but want to make my workout most effective, I plan to add 2 brutal HIITs into my week.

Just want some recommendation from you guys what your toughest FB HIITs are? Ones that are most tiring, sweaty, dying, nearly seeing death during the workout, else.

For me, ones with Daniel are very tough. LOL. However, I'd like to hear about yours too!