The Arbitrator may be heavily injured and screaming hoarsely from his mouth - or more precisely, his mouthpiece - but his movement speed did not seem affected in the slightest. He accelerated to an incredible speed in an instant!
Sheyan had miscalculated. There was a slight opening after he performed the 'Beast of Corrosion', and the Predator seized that opportunity to escape!
To be precise, what Sheyan failed to take into account was how incredible the Arbitrator's armour was.
The armour had provided extremely strong protection for the Arbitrator at critical moments and carried various powerful abilities, but it was also astonishingly heavy, so much so that an ordinary Predator would not even be able to move freely in it.