This is some basic information on the steam achievements for the Warhammer 40,000: Sanctus Reach game. Most of them are self-explanatory. They can be unlocked on any difficulty so set it to the easiest if you are having trouble. Ironman mode is not required for any achievement.

You WILL need to own two of the three DLC because they have exclusive units.

One required DLC is called "Sons of Cadia"
https://store.steampowered.com/app/716660/Warhammer_40000_Sanctus_Reach__Sons_of_Cadia/
https://steamdb.info/app/716660/
This DLC gives you access to play as or against the Astra Militarum faction. They have two achievements.

Quis Custodiet Ipsos Custodes?
Kill 100 Astra Militarum
I created a custom skirmish campaign where I only fought Astra Militarum. It unlocked around the 10th or 11th mission. Just kill 100 units of any type. You will average around 7-14 units on most missions.

That's Heavy Dude...
Destroy a Shadowsword

The Shadowsword is a rare Astra Militarum tank unit that you can force an encounter with by using the map editor. Killing rare units on user created levels still counts toward achievements like this one. I personally encountered one in a custom skirmish.














Moving on to the second required DLC...

The second required DLC is called "Horrors of the Warp"
https://store.steampowered.com/app/841150/Warhammer_40000_Sanctus_Reach__Horrors_of_the_Warp/
https://steamdb.info/app/841150/
This DLC gives you access to play as or against the Chaos faction. They have two achievements.

That’ll Tzeentch You!
Kill 100 Chaos units

Not So Thirsty Now!
Destroy a Lord of Skulls
The Lord of Skulls is a rare Chaos unit. I used the map editor for this one.










That's it for DLC achievements.


Play Freeblade!
Kill a Freeblade
The Freeblade is a rare Space Wolves unit. I only encountered one in my custom skirmish. The map editor is faster.


Lupophobia
Kill 100 Space Wolves
Make a custom skirmish campaign if you are having trouble with this one

Ork's Bane
Kill 100 Orks
Orc DLC not required

Shazbot
Kill a Morkanout
The Morkanout (Morkanaut?) is a rare orc unit. Possible encounter in campaigns. Map editor is faster. Orc DLC not required



That's Good Barbecue
Kill 25 units with flame attacks
The Space Wolves faction have multiple units with flame attacks. Small orc, astra, and chaos units seem to burn the best.

Chicken Dinner
Win a battle
This will be the first achievement you get and is unmissable.

Street Fighting
Win a multiplayer game
This is the one and only achievement that requires playing the multiplayer mode. User Hyrax explains how to unlock this by yourself.
"You can do this with hotseat as well. Just create a multiplayer game and join it yourself and play until you win (you control both sides)."
This can also be boosted with another player by creating a password protected game with map and army settings set to small. Meet in the middle and have the loser pick only one unit for their army. The winner can pick a couple and quickly kill the enemy unit to win.

All The Toys
Win a sandbox game
Start a skirmish game, and choose "Sandbox" for your army list. That will get you into a sandbox battle. Thanks to PipFromSlitherine for the info on this achievement.