We definitely need a sticky for these challenges. I haven't tried many because I'm grinding out to rank 50 to get my plat. But I have another challenge, and this one should be a little more difficult (I have a video link for the completion too).

Flawless Green Feisar
Complete the Feisar Prototype challenge in 2048 using only green weapons. *Note, you can absorb any weapon, you just can't use offensive weapons*
Pass: Complete with a time less than 8.00.00
Elite Pass: Complete with a time less than 7.52.50

Video link: https://www.youtube.com/watch?v=8-Rad6PtQjI