Ssak—
A Khrusam's head flew off the sky while its body dropped to the ground. He's one of the aliens in front who was caught off guard by Wallace's sudden appearance.
The latter's Void Phase is not just a quick movement but instantaneous movement using unexplainable magic.
Even if they have their third eyes opened, they would still miss his sudden appearance if they weren't prepared at all.
Aside from that, since Wallace was using his full strength at the start of their battle, they didn't have time to gather enough Death Energy from their Corpse Furnace.
Boom! Boom!
Wallace targeted the Furnace after realizing that they were easier to deal with than the aliens in the spaceships at the State of Kazan.
'Hmph! Want to escape?' He saw the three remaining Khrusams move back to their spaceships while the Marauder Gears and Mech Frames are covering them.