Big thanks to both Holodrone and Warlord K1ng for helping me put together this solution!
The Overachiever achievement requires you to acquire all fourteen medals related to the co-op campaign. Most of these require little effort, but some can be absolutely stubborn to unlock.
It appears that selecting 'Restart Mission' and 'Abort Mission' do NOT
always save your medals, so it is highly recommended that you complete the level over quitting. If you must quit, I would suggest being the host and dying before selecting the quit option to optimize the chance of the medal staying completed. Because of this, I would also suggest that you complete 'Brick Wall' last; the achievement unlocks after the final medal has been earned, so doing this one last will guarantee that you unlock the achievement without fear of losing the extra effort.
If you have a suggestion or revision to make, please drop me a comment! I enjoy all forms of feedback and love collaborating with other users to create the best solution possible for everyone. Please express yourselves! :)
_____________- Kill Related -Killpower
: Kill 20 enemies within 3 seconds of each other.Killociraptor
: Kill 30 enemies within 3 seconds of each other.Killdiculous
: Kill 40 enemies within 3 seconds of each other.Killowhat?!
: Kill 50 enemies within 3 seconds of each other.
These four medals are probably the easiest of the bunch, simply because there are so many enemies that appear towards the end a level. If you find yourself having trouble getting these, try having your co-op partner help you get to around the one minute mark on 'Checkpoint' (the first level) and let you mop of most of the kills.Invincible
: Kill 30 enemies in a row without being hit.Inconceivable
: Kill 40 enemies in a row without being hit.Unfrigginbelievable
: Kill 50 enemies in a row without being hit.
These three are relatively similar to the previous four, but they involve you killing a set number of enemies without taking any sort of damage (time is not required). During my adventures with the co-op mode, I usually got to around an Inconceivable before a humanoid form shot me and reset my counter. If you find yourself having trouble, consult the 'Kill it with fire' medal video below.
_____________- Miscellaneous -Repellent
: Prevent infection until your partner gets infected.
In order to receive this medal, your partner must be the first person to become "infected". Infection occurs when a golden infection form latches on to your player and begins to damage your health (only teammate assistance or enemy grenades can kill them). Simply choose a level and have your partner become infected as soon as possible.Kill it with fire
: Kill 50 enemies with fire without being hit.
This medal actually has more restrictive requirements than it hints at. For this medal, you must kill fifty enemies with fire without killing enemies with any other weapons. This might appear difficult at first but it actually is remarkable easy. Load up the second level (Holding the Fort) and collect the Firebomb grenades around the starting area. Head north and position yourself above the button and toss a firebomb grenade at the north gate as you see the enemies spawn; have your partner sit below and watch for golden infection forms and prevent them from reaching you. Roughly four waves of infection forms will spawn, continue tossing firebombs as necessary until the medal appears. This will also help with the Unfriggenbelievable medal at the same time.
Here is a video of this method in action!
Here is an alternative method that can be done on 'Power Net' (the fifth co-op mission). This method is also perfect for boosting the Extermination
achievement as well.
_____________- Armor Ability Related -Medic
: Heal your partner with a Regeneration Field.
This medal simply requires you have your partner step into a Regeneration Field when you have it deployed. You can load up 'Holding the Fort' (the second level) and begin with Loadout A. Once the level begins, tap LB to bring up your field and have your partner step in it.Brick Wall
: Block 10 Explosion or Infection Forms with your Hardlight Shield before it depletes.
This one is slightly misleading in that it does not tell you that taking damage actually resets your counter. Start up 'Power Net' and go pick up the Hardlight shield in the shielded area to the north-east (you'll need your partner to open up the door by pressing the switches on the floor). Head to the north-east corner of the level (the very top-right) and move west until you run into a Flood spawning hive. Sitting in the top left corner, right against the hive, use your Hardlight shield and point downward to block bullets and infection forms. While you are doing that, have your teammate kill enemies by the corner of the map (focusing on infection forms that are not going for you). With proper timing and a bit of luck, six or so infection forms will continue spawning and will detonate immediately as you are sitting next to their hive. They will then respawn again, giving you enough to earn the brick wall medal.
Here is a clip of where you should position yourself:Long Distance
: Teleport back to your partner over a distance of 75 meters.
This medal can be very easily done on 'Power Net' (the fifth co-op level). Start up the level with Loadout B. Once the level has begun, venture in separate directions, following the bottom edge of the map. Once you both have reached the left/right corners, tap the left bumper to teleport to your partner to unlock the medal.Bug Off
: Use the Overshield to prevent infection.
For this medal to unlock, you must activate your Overshield ability and then have a golden infection form latch onto you. An easy place to unlock this is 'Checkpoint' (the first co-op level). Select Loadout A and move to the eastern part of the bridge (all the way to the shield at the end of the level). Defend for a minute or so and golden infection forms will come through the wall at the end. Activate your Overshield ability and run towards them. Once they latch onto you, they will detonate and the medal will be awarded.Perimeter
: Use Repel as a safe zone for your partner.
This is much like the Medic medal, but you must use a Repel ability, rather than the Regeneration Field. Start up 'Checkpoint' (the first level) with Loadout B, and press LB to activate your Repel ability; have your partner walk into the smoke and medal will appear.