Awesome / Sudden Contact

• Tassadar's Heroic Sacrifice in Chapter 39. While his death in the original was well executed, it goes into depth here as to just what he experiences in his last moments.
  Tassadar: They should... have sent a poet!
• Liara ultimately saves the entire galaxy by the end of Sudden Contact. Even when she's under Sovereign's control, she manages to convince Legion to rally the geth in an alliance with the Council to ward off the invading zerg, eventually even gaining the allegiance of the protoss, who destroy both the Overmind and Sovereign. With just words, Liara manages to save the galaxy from being assimilated by the zerg and prevents the Reapers from returning. Sadly, no one else ever realizes it.
• While it's mostly offscreen, the fight between Liara and Nova in chapter 25 of Sudden Supremacy is this on both sides; Liara managed to defeat one of only two known class-10 terran psychics, and Nova for managing to fight off Liara at all.
• Kasumi Goto managed to sneak into the three Waygates orbiting Moria itself and blew them all up to get back at Hock. In retrospect, Moria is the KMC capital world, and the Waygates are some of the most valuable assets they have; meaning, Kasumi snuck through all of the security that that implies to plant the bombs.
• Javik is able to threaten Harbinger, the leader of the Reapers, into launching their invasion prematurely when he reveals the Hybrids to them. This is the first time that a Reaper has displayed anything remotely close to fear.