This is one of the secret cheevos and it is called "Forged alliance"
This is a story related cheevo and therefore it can not be missed.
This will be awarded upon completion of episode 1: Low life / low tech
This episode is quite simple and very linear so you wont get lost and there are a few other cheevos available to you during this episode..
Halfway through the episode you will face a enemy called a skinner and if you avoid his charge attack 5 times in a row you can earn the following cheevo.
You know your at the end of the mission when you reach the bar and are talking to headache tommy and you will be attacked by an assassin. Be sure to get the following 2 cheevos during the memory sequence with the assassin.