To do this without losing your entire squad, focus on killing enemies as quickly as possible instead of rescuing the civilians one-by-one. Also, try drawing the enemies attention to have them attack you instead of the civilians.
Melee Like to Melee
While it sounds straightforward, recognize that melee forces will try to attack you to your face no matter how ridiculous it is. Stun troopers who should stay under cover will try to attack your soldiers up close, even if it puts them in a horrible position. Be prepared for this. Also, remember that many melee units can attack on the same turn as when they first see you. Don't be surprised when an enemy appears and instantly manages to land a blow; this is why you should consistently overwatch, especially if there are signs that kind of enemy is around (for example, Faceless on missions where you are defending civilians).
Stop the Aliens
Just like the predecessor you have to stop the Aliens from completing their project call 'Project Avatar'. This Project is for the end of the world and you need to stop it before the countdown. Here they simplest ways to stop the countdown is by assaulting an enemy facility or completing the Story Objective. While Assaulting the facility is very easy and brings down the progress bar instantly and you get the time to expand other regions and build more power.
Super Grenadier
Change nickname to Beaglerush.
Super Psi Operative
Change name to Sid Meier.
Super Ranger
Change name to Peter Van Doorn.
Terminate Sectoid
Turn your Main goal to terminate all the Sectoid as these are also a threat to your squad. You must start this at a very early stage and whenever you get the opportunities to target them. You can find their corpse at the back of the base so once you are done taking down, head directly to the research lab. Now start helping Dr. Tygan to perform Sectoid Autopsy. This is a time-consuming process so if you want you can continue with side objectives until he finishes the work.
Various Achievements
Complete the following achievements to unlock Xbox Live Gamerscore points.
Achievement
How to unlock
Type
A New Alliance
Complete the Lost and Abandoned mission
10
A Rival Silenced
Permanently defeat one of the Chosen
20
Born in the Darkness
Get four kills from Shadow mode with a Reaper in a single mission
10
Can't Stop the Fighting
Perform three offensive actions against the same target with a Skirmisher in a single turn
15
Circle of Psi
Raise a Templar to maximum Focus level, spend it all, and reach the max again in a single mission
20
Fully Operational Resistance
Raise XCOM's influence with all three factions to High in a single game
30
It Takes Two
Form a level 3 bond between two soldiers
20
No One Left Behind
Rescue a soldier who was captured by the Chosen
15
Weary Warriors
Complete a mission with all Tired soldiers and no casualties
Easy "Heroes Of The Resistance...