U can use devastator when u are in critical m*** or in adrenaline surge.

use my trainer i uploaded

There are 3 different Devastator attacks i think and all of them have an "In Air" version.
The First one is the "Tendril Barrage" wich shoots alot of tendrils from Alex's Body
Eleminating Hundreds of enemies on screen.

You use it by holding down "E" and "Right Click"

The next one is the "Critical Pain" devestator attack, this is the most powerful
devestator move, Alex shoots out a something like a consentrated beam of mass from his
palms. However you can only hit the enemies directly in front of you.

you use it by holding down "E" and "Left Click"

The Next and Last Devastator move is the "Graveyard Groundspike" Alex slams his fist in
the ground and alot of spike's shoots up from the ground, its very effective against Tanks
or rather "Armor" Generally. It also deals alot of damage to buildings if you stand on top
of them.

you use this by holding down both "Left click" and "Right Click" at the same time.

"In Air" Devastator moves: its pretty easy actually you just use the devastator moves
while your in the air.