Level 73

Total Experience Required 2,393,011 [confirmed]

Level 100 progress: 35.06%

This is roughly:
Killing 7,977 people in Warzone, or...
Killing 8,140 people in Execution, or...
Killing 6,760 people in Wingman, or...
Scoring 1,709,294 points in Guardian, or...
Scoring 5,202,198 points in Annex, or...
Scoring 3,148,699 points in Submission.

Horde (TU4)

Completing 11,966 waves on Casual, or...
Completing 7,977 waves on Normal, or...
Completing 5,983 waves on Hardcore, or...
Completing 4,787 waves on Insane.

Or a combination of the above. Have fun!