Nice. Now, put together a non-bugged loadout that can do it
I was wondering why and how it had Front Shield Emitter.
But really, two Phase Beams is more than enough. With regular crew it can barely last long enough against the rear autocannons to knock out its engines, with Veteran or Elite it takes so little damage that it can easily camp the engines with no problem.
Edit: My bad, once it figures out its range (with Optics) it can actually kill the Onslaught without even being shot by the rear guns.