Warhammer 40,000: Space Marine 2

You will run in to Scarab Occult Terminator's for the first time in Mission 6 - Dawn’s Descent.
3 of them will be on an elevator in the mines.
To unlock Know No Fear parry blue attack and immedietly press block again to parry second attack.

This is going to be easier in Operations, because you can create a custom Marine tailored specifically to this achievement.

Melee weapons that have their Defence type listed as "Fencing" have the largest Perfect Parry window. The Vanguard class also gets a perk at level 3 called "Duelist" that further increases your Perfect Parry window by an additional 50% on top of the Fencing weapon.

So, pick either a Fencing Chainsword or Combat Knife, whichever you prefer, equip the Duelist perk, and start up Operation 3, 4 or 5, whichever you prefer, as these are the maps that can spawn Chaos enemies. Then it's as simple as finding a Terminator, get in close to tempt him into going for his melee lunge, then parry his attacks. My reaction time for parrying isn't the best, but I managed to get this on my first try, so if I can do it, anyone can.

Ok so what you are going to want to do is go to the final mission for the campaign and you are going to go a bit deep into it and you will finally get to this big elevator thingy fight off some people around and then 3 people will come up an elevator. Two people with Knives and one with a gun knife, YOU HAVE TO PARRY 2 ATTACKS FROM THE GUYS THATS ARE CALLED THE TERMINATORS WITH SWORDS, not the ones that have like a big machine gun and a sword. Has to be the terminator with a pistol and a sword and trust me you will know who they are bc they are annoying.