The phrase "biggest challenge" refers to the most difficult or demanding obstacle that someone faces. It signifies the greatest problem or hurdle that needs to be overcome. Full definition
The lack of verified identities among buyers is one of biggest challenges for heavily regulated businesses who want to work with cryptocurrencies like bitcoin. (ibtimes.com)
We start 2016 as we started 2015 — with big challenges for the health system and uncertainty as to how governments will meet them. (croakey.org)
This will help in taking bigger challenges in my field wherein I will be able to use my expertise and proficiency level in creating unparalleled and unique designs. (sampleresumeobjectives.org)