Chen verbally bitchslapping the fanatics who were willing to turn off the nuclear reactor on the Ark, especially if you failed the mission. "Who told you to do this? This...this wasn't the plan! I never meant it! It was a BLUFF! WE WERE BLUFFING! I SAID THREATEN TO, NOT ACTUALLY DO IT! WHAT WERE YOU THINKING?!"
Finishing Security Day 3, because it is so difficult otherwise.
On a similar note, finishing Resistance Day 2. You will be yelling at Nechayev to hurry the hell up. Why you don't just have a heavy toss the wounded pilot onto his shoulders is beyond me.