The most efficient way to unlock Peak Condition is through multiplayer. En route you'll also net:
The Explorer achievement in Mass Effect 3 worth 17 pointsComplete three multiplayer matches or five N7 missions.
The Tourist achievement in Mass Effect 3 worth 5 pointsComplete one multiplayer match or two N7 missions.
if not already unlocked through single player progression.
This requires you to rank one class up to lvl 20, your N7 rating is separate and not of consequence to this achievement.
Tactic wise it's proves most effective to roll with a diverse four-man squad, preferably with mics for communication. I mention diverse because there's not much benefit to having four soldiers and with the same skill set. You will start to cut through waves fairly quickly once you have a range of upgraded abilities working for you. - Someone able to neutralize barriers
-Someone able to take down shields
-Someone able to penetrate armor.
Our squad consisted of mainly: Adept, Engineer, Soldier and Infiltrator
Now speaking to the missions. If you're strictly looking to rank up quickly unknown location (10% xp bonus) unknown enemy (15% xp bonus) and bronze missions are the way to go.
Once you get into the groove you can knock out 10 waves plus extraction in 15-17 mins and usually net 140k-170k in xp. Silver missions are doable with a good group and although the bring in more credits the xp rewards aren't enough of a jump to warrant spending double the time it takes to complete bronze missions. If you can roll through Gold maps...then you prob have no use for this guide and I don't really need to entertain that as an option lol.
Two big things to concentrate on are:
- Not going down! You'll get xp bonuses after completing 3 (2500 xp), 5 (5000 xp) and 10 (15,000 xp) waves consecutively if none of your squad go down at all.
- When it's time for extraction you don't all have to been in the zone during the countdown BUT ensure you're all there when the counter expires to net another 15,000 xp bonus.
All in all I spent about 7hrs working on this and once you've hit lvl 20 if you're comfortable promoting them (similar to prestiging) you can also attain Solution for Battle Scarred in Mass Effect 3