The Angel 013 was developed as a larger version of the successful ARM, which was a lighter mech. The Angel 013 has upgraded weapons, is massive, and is armoured very heavily. The mecha is a sight that people fear, including some of the toughest militaries and forces.
The vehicle is unlocked by completing "A New Dawn" as part of the Corporate Warfare DLC.
Essentially a really op Just Cause 3 mech, with a larger GRIP, more guns and a lot more armor.