Here is how Nighlock pursues and defeats some Chitauri scouts and fights against Dark Eagle in Battle of the Superhumans Part 1.
(we see two Chitauri scouts running through the streets)
N.I.G.H: Sir, I have located the scouts.
Nighlock: Where are they?
N.I.G.H: Right below us.
(Nighlock attacks the scouts, and kills them)
(rockets are heard, and Nighlock clenches his fist)
(a glider flies in and Dark Eagle is on it)
Dark Eagle:(backflips off of it)
Nighlock: You shouldn't have come here, Dark Eagle.(walks up to him)
Dark Eagle: You're right, Nighlock. I shouldn't. But you interfered in these scouts mission to get me the information I required.
(they start fighting)
(as they fight, the street gets damaged)
Dark Eagle:(takes off his cape to reveal two large black wings)
(Both take to the sky and fight)
(eventually, the Titan flies off, leaving Nighlock in the damaged street)
Nighlock:(to himself) All of our enemies have been really active. They're definitely up to something.
(sirens are heard, and Nighlock flies off)
(Battle of the Superhumans Part 1)