Transformers: Revenge of the Fallen

1 minute matches with 2 people will do. Can be done in player matches. Set the game mode to and you could even keep starting matches while their away(30 seconds If they don't ready up)

Autobots:
Ironhide
Optimus Prime
Powered-up Optimus
Bumblebee
Ratchet
Protectobot
Aerialbot
Breakaway

Decepticons
Megatron
Megatron (Flight)
Seeker
Long Haul
Sideways
Grindor
Starscream

Please note that this achievement has issues unlocking sometimes, it is best to as stated above make a list of all characters and tick them off as you go through them. To avoid this achievement not unlocking, try to win with all 15 characters in the same game type e.g DeathMatch.

I won with 14 characters in DeathMatch and one in Control Point, and it didn't unlock but when I won with that same character in DeathMatch the achievement unlocked.

As the achievement description states there are a total of 15 Transformers you need to win as to unlock this achievement, here's a list of them;

Autobots;
• Optimus Prime
• Optimus Prime (Powered-Up)
• Ironhide
• Bumblebee
• Ratchet
• Breakaway
• Protectobot
• Aerialbot

Decepticons;
• Megatron
• Megatron (Flight)
• Starscream
• Long Haul
• Sideways
• Grindor
• Seeker

You may find it beneficial to copy that list into a word pad and mark them off as you win a match as them to help prevent you missing one!

Managing to fulfil the achievement requirements without boosting now is slim to none, not impossible, just very unlikely!

With that in mind get searching, you can set up a gaming session here; http://bit.ly/hBVCpm and try to find someone that way or you could ask around on the forums!