The way Johnson lit up Khabib, I think Khabib has the least chance of doing well against Conor. Doubt the fight would even go 1 minute.
Ferguson is a much tougher prospect because of his reach advantage and height, but then Ferguson over commits and gets caught too much so he's getting KO'd too.
Nate's the only one with good enough boxing to stand with Conor, and even he got sat on his ass multiple times.
Woodley is the biggest challenge. The explosiveness and power could not be withstood if he caught him