Go into the mission with fully-stocked Mika tickets, and if possible, a fully-upgraded "Healing" skill (so that pressing LB will let you exchange blood for health).
This is basically the same map as Mission 4 -- or very near to it. Just with a different chain of events and much tougher enemies.
In the first room, defeat the enemies and avoid the purple "dark matter" tornadoes (basically, don't fight where they spawn, and don't walk into them). After a couple of enemy waves, a door will open. Continue to the next room for another wave of enemies, then go through the picture.
Fight one purple/gold guy in this room, then go through the door. Go down the stairs and bust the vases to reveal a drillable place in the wall. If you don't have the drill, it can be obtained the first time you "win" a Gigolo mission (you probably already have it by now). If you're lacking blood, you can use the wall panel (not the painting), go through the door it opens, and get a small amount of blood by breaking vases. Inside the room behind the breakable wall you'll find goodies, but also an eyeball orb creature, which you can run from and go through the painting. You can skip this entirely by just going through the painting to begin with.
You'll come to a balcony-type room that's square, overlooking an area below. Defeat more enemies, then go through the door on the other side.
In a room with a blue floor, enemies will bust out of the pots. Kill them all, then enter the picture on the wall to the left of the closed door. This leads to more enemies, more dark matter tornadoes you should avoid, and after defeating them, another open door.
You'll come to a room with many benches, and an open door leading to a hallway where there is an enemy that shoots a laser at you. Kill him, then enter the next room. Another door here leads to a hallway, which then leads to another large room with stairs on both sides.
There are more enemies and dark matter. This room is infested with the two types of eyeball creatures, too. After defeating them all, a painting will open on the lower level, in the middle of the wall.
This brings you to a large room with a gold/purple enemy and a large spikey-club-wielding brute. After defeating them both, you'll have to fight another club-carrying brute. It's hard to refill blood by fighting the big guys, but there are a couple pots on either side at one end that have small amounts of blood -- enough for a full rose, at least. One tactic is to keep your distance, keep shooting, and try to be in a position to quickly break a vase, collect the blood, and do the finisher. You can take out the big brutes with melee attacks rather than shooting them, but they have a wide reach, and dodging successfully can be tough. Hopefully, by this final mission in the game, you've come up with an effective strategy against them.
Once this is done, you're whisked away automatically to the final boss battle.
The boss battle happens in three stages. Pretty much the only tactic you need is to dodge and dodge-burst as much as possible (B, then X's when prompted if you've triggered a dodge burst). Slash away as much as you can, but try to leave one full blood rose available to finish him in each round. With good timing and a little luck, you can chain together several dodge-bursts and do heavy damage in a short amount of time.
Things change some in each of the three stages, but the tactic remains the same. In the second stage, he will throw slow-moving orange energy globes at you, but they're not hard to avoid. He gets faster and more aggressive, especially in the final stage, but keep dodging and attacking and taking advantage of dodge bursts. Each round ends with the RT + X finisher, so be sure you've got blood remaining for that. Up-close melee hits while he's down will refill it, sometimes quickly enough to do the finisher before you lose the opportunity.
On "Very Hard" mode, I still used 3 Mika tickets to revive and get through the three rounds of this fight.
And that's the end. Ending cut-scenes, and so forth. If I recall correctly, this achievement will unlock at the mission results screen, as with others. However, if you played on Normal, Hard, or Very Hard (after finishing once on Normal or Hard), you'll get the corresponding difficulty-based achievement (which don't stack) after the credits.