Level 52

Total Experience Required 715,858

Level 100 progress: 10.49%

This is roughly the same as:

Killing 1,194 people in Warzone, or...
Killing 1,218 people in Execution, or...
Killing 1,012 people in Wingman, or...
Scoring 255,664 points in Guardian, or...
Scoring 778,107 points in Annex, or...
Scoring 470,960 points in Submission.

Horde (TU4)

Completing 1,790 waves on Casual, or...
Completing 1,194 waves on Normal, or...
Completing 895 waves on Hardcore, or...
Completing 716 waves on Insane.

Or a combination of the above. Have fun!