This achievement needs XP and you can boost XP with only 2 players, in a treasure hunt in team match. The best way for boosting XP I know is the kill-respawn trick : First, define a killer and a respawner. Then, find a place where respawner can be killed as soon as he respawns, always on the same place. For that, the killer must be far enough and consequently, use a weapon adapted for this exercice (the sniper is best). Look at the video for an example.
A game lasts 10 minutes, the killer should shoot the respawner during all this time and grab all the statues at the very end. You can hope at least 100-120 kills a game, that brings between 15 000 and 18 000 XP. Repeat and you will get the achievements Commando and Changeling, and endly reach the last rank, the rank 35 (307 500 XP)