Mission list is here if someone having a hard time trying to remember the name
http://sto.gamepedia.com/List_of_missions
For me It's
Klingon- Alpha
Romulan - Mind Game
TOS - um ? I honesty didn't expect to draw a blank here, I don't think any of theexclusive ones were that good but maybe “The Taurean Affair”? if I had to pick.
Federation - Sphere of Influence
Comments
'Midnight' ended the Iconian War on the right note, combining elements of science fiction and mutual understanding (the hallmark combination of Star Trek) to bring the conflict to an amicable end. 'Ragnarok' was the opposite, but in the right way; it brought the Temporal (no longer Cold) War to an end in a way that felt consistent with the lore and tone established by the television series (appearing to draw the right inspiration from 'What You Leave Behind,' as well as building on the glimpse of the Battle of Procyon V from 'Azati Prine'), making for a satisfying and epic conclusion.
For the simple reason you get your KDF boarding party, cleave through the Starfleet crew, corner the ship's captain, beat the s**t out of him for the codes, then opt to shoot him still, beam out, and blow the ship away.
Then you round some support and go to the Mars Shipyards of the Federation and cause havoc.
This mission screamed "Klingon."