Mistral's interesting because she's essentially the first human boss of MGR:R, and the first chance you have to fight a cyborg similar to yourself (for context: in MGR, you play as the cybord Raiden, capable of slicing through almost any substance besides cats). It starts off in an arena-style boss fight, but progresses on to various other parts of the map.
Here's a basic breakdown of the level:
1- The fight's introduction: you run out onto a raised platform, where Mistral greets you with a cutscene explaining her backstory. She reveals herself as a cyborg when she absorbs multiple arms from the small Gekkos around her, and attacks you. In this area it's a lot of run and slash-- both you and Mistral are restricted to that area, and as it's fairly close quarters the action is super fast. You have to try and slice both her arms and the polearm she's constructed out of arms (yes, the pun doesn't escape me. You could say she's pretty well armed). You can build up bonus points by slicing up the Gekkos and attack her head-on. Once you've done this enough, you can do a special attack that kicks her off the platform onto level...
2- which is a far smaller horizontal pipe. Mistral regenerates her arms and begins to attack you with more long-range whip attacks constructed exactly for this environment-- there's no way to jump to the side, so you must jump up, run under, or parry. She can also access the higher ground to throw the Gekkos at you as projectiles. Once you hit her enough, the pipes underneath you are sliced apart and you run down them to level...
3- which is a more open area on the power plant ground, complete with hiding spots behind pillars and more of an up-and-down explorable area. Here Mistral can use both her long and short range attacks, including a new whip attack that brings you closer to her.
Once you've hit her enough times, and you've timed your attack correctly, you can force her to accidentally pierce a tank of liquid nitrogen. You slice the tank open and Mistral is frozen immediately. It's short work to cut her up into tiny pieces.
What I like best about this Boss Battle is how its locations help explain the new attacks as Mistral uses them. Metal Gear Revengeance is a super fast-paced game, and being able to read the environment to adapt your playstyle to its limitations is very important. Having the other character respond to such changes is pivotal.