Ghostrunner

The fight is pretty straight forward.

First phase is dodging 3 rounds of his AOE missiles, then a countering game.

Second phase is basically the same but with a slightly different parrying pattern, not hard to figure out though (both are way easier than Hel in main campaign)

In third phase he stays in the air, constantly shooting his AOE missiles. Additionally, his bodyguards keep spawning, the goal is to use them to fill up your Rage meter. Kill one guy, jump, target midair and fire a Surge at Bakunin (there's an arrow on the screen pointing his direction from the player). One kill fills up your Rage meter enough to have one shot of your Surge. Kill his bodyguard, jump, aim, shoot, repeat. All that while evading his AOE attacks. I recommend staying in constant move, preferably jumping a lot, so that the bodyguards can't jump at you.

Also, don't worry if you die, especially in third phase, you're being directly respawned during that phase.

Here's me doing it, if my guide isn't clear enough: