Using the strat developed by youtuber Feya Chan ( @feyachan4758 ).

All you need is to use the glitched rocket launcher and abuse reflex. There's actually a sweet spot, and if you shoot where I did you'll get the one shot somewhat consistently.

The launcher I used: Base: FB MR R-LAUNCHER (GRADE 5) Magazine: 12GA MAG x6

00:01.167 - Run starts (last dark frame) 00:06.767 - Run ends (Last hit / "Objective Complete" text appears)

If there's something wrong with my timing I'll fix it as soon as possible.