In this Wonder Woman clip provided to IGN, we see Diana barging in on the military operation General Ludendorff is overseeing.
From there the intense fight sequence breaks out, and even though Diana has trained as a warrior for gods know how long on Themyscira, Ludendorff, a normal human by all appearances, puts up a good fight.
What he didn’t count on what Diana being able to deflect his bullet straight back at his gun.
He appears to recognize her, which would make sense given that earlier Wonder Woman trailers showed those two at the same party, but he has no problem with swiftly eliminating her.