Iron Man 2
51 Achievements
12-15h
Omega Man
Defeat 100 enemies as War Machine while using the Omega System.
2.9%
How to unlock the Omega Man achievement in Iron Man 2 - Definitive Guide
EDIT: with thanks to PrimeBigTime
If you hit every laser on the way down first before engaging enemies instead of engaging after each set of lasers, you will have over 20 enemies on the screen at once. This makes the Omega System and Iron Man's Invincibility last longer, and also destroys more enemies with each shot of the Unibeam.
Once you go outside, you get the option to once again use your "power" but wait until you have activated to console to narrow down the SHIELD agents position. If you haven't killed anyone since going outside that means there is a lotta people waiting for you when you start heading towards her position so trigger it and lay waste.
Welcome to the most boring part of the game. Luckily for you there is a great place you can farm all these trophies. That place is on Mission 4. Firstly hack the 2 terminals then fly down the shaft with the green lasers, making sure you hit all 3 layers on the way down. (Yes deliberately hit the lasers, as this will bring out a ton of enemies).
Once you reach the bottom you will be attacked by 20-25 robots. Now just kill them with the weapon your trying to get the trophy for. When they all die a door will open and about 8 more robots will come. Go through the door they came from and destroy the 8 turrets on the wall. (These count as kills). As soon as they die it will come up as "Checkpoint reached". Now press start and go to "Save last Checkpoint". Once it saves quit back to Headquarters and repeat the process.
Start level 4, activate the first panel, then the second. Then hit the green rays on all three levels. About 20-25 robots will appear, kill them with the weapon for which you need a trophy. Then several more robots will appear, kill them as well. Then kill 8 cannons (they also count as kills). After this the message “Checkpoint reached” will appear, then press start and select “Save last Checkpoint”. Then return to Headquarters and repeat the process.