Level 53

Total Experience Required 764,738 [confirmed]

Level 100 progress: 11.2%

This is roughly:
Killing 2,550 people in Warzone, or...
Killing 2,602 people in Execution, or...
Killing 2,161 people in Wingman, or...
Scoring 546,242 points in Guardian, or...
Scoring 1,662,474 points in Annex, or...
Scoring 1,006,235 points in Submission.

Horde (TU4)

Completing 3,824 waves on Casual, or...
Completing 2,550 waves on Normal, or...
Completing 1,912 waves on Hardcore, or...
Completing 1,530 waves on Insane.

Or a combination of the above. Have fun!