Vanquish is an awesome game. Unequivocally so, in my opinion. I thoroughly enjoyed finishing this third-person action-shooter on its “Hard” difficulty from the get go, although this was due to the related achievements you unlock for doing so.
So, here are some common sense tips and/or things to at least bear in mind, if you decide to pursue this avenue yourself.
1. Choose your preferred weapons to stick with.
During my run, my weapons of choice were the assault rifle, heavy machine gun, and – depending on scenario – either the rocket launcher or sniper rifle. The assault rifle is an obvious choice, its rapid fire and constant availability throughout the game means you’ll never be short on ammo, or the opportunity to upgrade it. Same applies to the heavy machine gun, but with less rapid fire and scope for the more distant enemies.
2. Upgrade your weapon choices as much as possible.
Although the main concern is staying alive (naturally), ensure to raid as many weapon boxes as possible on every mission. It is usually safer to do this once an area is cleared, if possible, as is the best opportunity not just to reload, but maybe gain two or three star ranks on your weapons. Not many weapon drops occur from destroyed enemies on hard difficulty. It’s worth noting that when I got to end of the game on this difficulty, none of my weapons were at the maximum rank. However, this was my first run through. It is definitely achievable.
3. Prepare to die. A lot.
If this is also your first run though the game, then some of the set pieces will require a trial and error approach, you will die quite a lot. Believe it. But, keep going, it only gets more and more difficult, so suck it up.
4. Use AR mode as much as possible.
Performed by using the evade command whilst targeting, AR (Augmented Reality) Mode slows down time, and is the best way to quickly target and achieve those critical hits. It can be a lifesaver against an Argus robot, for sure. Try also not to max out the AR bar; it’s quicker to recharge it than letting the suit overheat, as will leave you more exposed. Of course, if you do take a critical hit, AR Mode automatically activates, but will max out, so find cover!
5. Never underestimate cover.
Using cover locations is vital to stay alive, particularly on this difficulty. The R.Is are more accurate with their aim, and you take less damage to die. Using cover works the same as any Gears of War game; pressing the command button when standing in front of a bunker, or wall, etc. Keep moving though, as cover locations will be destroyed eventually if they take a lot of firepower.
Overall
Finishing the game on hard difficulty, even without obtaining the act-based achievements, is worth 290 gamerpoints, and there are many more combat achievements you are sure to pick up along the way. If you’re up to it, you can go for the “Finish the game without dying once” achievement by returning to the title screen whenever you die, then select continue. Never pick the checkpoint option, as it will record this as a death. Good luck!