Here is the full list of all 21 Avenging Angel achievements.
Leave Outpost and enter Statue Forest
Complete Daedalus’ quest
Complete Rust in Pieces quest
Ask Daedalus a specific question
Find all journals
Tell Freya that she is one manipulative bitch
Find all weapons
Find all weapon mods
Find all blueprints
Craft an alchemical potion at any workbench
Craft any weapon at any workbench
Stagger a QingTing Commando at least once
Stagger Nemesis with electricity at least once
Install Antero in the Inner Sanctum Mainframe
Install Freya in the Inner Sanctum Mainframe
Collect all Guild Dog Tags
Complete the Words as Power sidequest
Complete the Pain & Despair sidequest
Complete the main story line
Use Vendortron
Defeat one BFG