Successfully complete the game to unlock Ragnarok in local multi-player mode. Successfully complete the game on any difficult setting to unlock a mech called Ymir. Note: The Ragnarok mech is a perfect blend of armor, firepower, and heat design as long you do not use the lava gun constantly. The Ymir has greater firepower than the regular chassis of Ragnarok. However, it generates a great deal more heat, making it a good choice for advanced players for to make short work of their opposition.
To easily avoid a PPC projectile when playing on Xbox Live, choose a mech that has jump jets. While the enemy is charging up their PPC, activate your jump jets. Once they fire, release the jump jets and the PPC will fly over you as you fall to the ground. This can be very effective against Mad Cats.
When playing as the Atlas in the lava area, at the end near the party, do not go into the area from the cave too far. It will activate several Mechs including an Atlas or two. Instead, destroy the helicopters with ease, then start destroying everything around that gets targeted. Eventually, you will find two Atlases in the back left corner. You will know that you are targeting them because it takes a lot to destroy them. Note: You should not be able to see them. Inch forward from the opening and you should be fine. You will face two mechs, a Madcat and a Belial. Also, the Atlases will not attack you in retaliation.
At the beginning of the level where you must kill the WOB's second in command, stay on the ledge. Do not fall or you will be slaughtered. Kill the stray Mech that is not one of the objectives. Next, walk further down the ledge until you reach a bridge. Use your radar to see when the objective Mech catapults are under the bridge, then blast the bridge. It should kill most of the Mechs. Then just finish off the survivors.
Before you destroy the ship that the leader tries to escape in, go to the back and destroy the bridge and tunnel. If you do not do this, a lot of reinforcements will come through the tunnel after you destroy the ship. To kill Ragnarok easily, shoot him until he gets by a barrel that explodes, then destroy the barrel. It weakens him a lot.
Go to a bridge that tanks cross. Fire at the tanks and kill destroy them. Next, shoot down the bridge. When you look back at the bridge, you will see the tanks' remains floating in mid-air.