Level 61

Total Experience Required 1,254,826

Level 100 progress: 18.38%

This is roughly the same as:

Killing 2,092 people in Warzone, or...
Killing 2,135 people in Execution, or...
Killing 1,773 people in Wingman, or...
Scoring 448,153 points in Guardian, or...
Scoring 1,363,942 points in Annex, or...
Scoring 825,544 points in Submission.

Horde (TU4)

Completing 3,138 waves on Casual, or...
Completing 2,092 waves on Normal, or...
Completing 1,569 waves on Hardcore, or...
Completing 1,255 waves on Insane.

Or a combination of the above. Have fun!